Globally, about 15% of newborns are born with a low birth weight (LBW) as a result of preterm birth or intrauterine growth restriction or both. Up to 70% of neonatal deaths occur in this group within the first 3 days after birth. Kangaroo Mother Care (KMC) applied after stabilization of the infant has been shown to reduce mortality by 40% among hospitalized infants with a birth weight of less than 2.0 kg. In these studies, infants were randomly assigned and KMC was initiated after about 3 days of age, when the majority of neonatal deaths would have already occurred. The aim of this trial is to evaluate the safety and efficacy of continuous KMC initiated as soon as possible after birth compared with the current recommendation of initiating continuous KMC after stabilization in neonates with a birth weight between 1.0 and less than 1.8 kg.This randomized controlled trial is being conducted in tertiary-care hospitals in five low- to middle-income countries (LMICs) in South Asia and sub-Saharan Africa. All pregnant women admitted to these hospitals for childbirth are pre-screened. After delivery, all neonates with a birth weight between 1.0 and less than 1.8 kg are screened for enrollment. Eligible infants are randomly assigned to intervention and control groups. The intervention consists of continuous skin-to-skin contact initiated as soon as possible after birth, promotion and support for early exclusive breastfeeding, and provision of health care for mother and baby with as little separation as possible. This efficacy trial will primarily evaluate the impact of KMC started immediately after birth on neonatal death (between enrollment and 72 h of age and deaths between enrollment and 28 days of age) and other key outcomes.This is the first large multi-country trial studying immediate KMC in LMICs. Implementation of this intervention has already resulted in an important enhancement of the paradigm shift in LMIC settings in which mothers are not separated from their baby in neonatal intensive care units (NICUs). The findings of this trial will have future global implications not only on how the LBW newborns are cared for immediately after birth but also for the dissemination of designing NICUs in accordance with the mother-neonatal intensive care unit (M-NICU) model.ACTRN12618001880235 (retrospectively registered).Clinical Trials Registry - India (CTRI): CTRI/2018/08/01536 (retrospectively registered); Australian New Zealand Clinical Trials Registry (ANZCTR):  Globally, about 15% of infants are low birth weight (LBW) as a result of preterm birth or intrauterine growth retardation or both, and 60 to 80% of deaths in the neonatal period occur in these LBW infants . The majSeveral interventions have been proven to be effective for improving survival of LBW infants, such as antenatal corticosteroids, breastfeeding, hygiene, case management of suspected infections, and hospital care of small babies, including Kangaroo Mother Care (KMC) . The WorKangaroo Mother Care: A Practical Guide recommends initiation of short KMC sessions when the baby starts to recover, even if the baby still requires medical treatment such as intravenous fluids or oxygen [The WHO publication r oxygen . It alsor oxygen . These bA recently updated Cochrane review reported 40% lower mortality in infants with a birth weight of less than 2.0 kg who were given KMC as compared with those who were given standard  care in hospitals at 40–41 weeks’ postmenstrual age  0.60, 95% confidence interval (CI) 0.39 to 0.92; eight trials, 1736 infants) . This reP <0.02) in the immediate SSC group. The neonates in the intervention group had significantly lower need for respiratory support, intravenous fluids, and antibiotic use during their hospital stay [KMC cannot influence deaths that happen before its initiation. Thus, the 40% mortality impact of KMC in enrolled infants would translate in practice to only about 13% impact on mortality in all babies with a birth weight of less than 2.0 kg. Only two small randomized controlled trials (RCTs) have evaluated the feasibility, safety, and effect on stabilization of initiating KMC immediately after birth. In the RCT from South Africa , SSC frotal stay .The impact of the KMC intervention could have been much larger had it been initiated immediately after birth. However, this has not been evaluated in LBW infants. Therefore, we aim to evaluate the safety and efficacy of continuous KMC initiated immediately after birth for neonates with a birth weight of 1.0 to less than 1.8 kg compared with initiating KMC after stabilization in improving survival. In this study, our main hypothesis is that those very small babies who are provided continuous KMC initiated immediately after birth will experience a reduced risk of death compared with a similar group in whom KMC is initiated only after stabilization.This is a multi-country, multi-center, non-blinded RCT to measure the effect of continuous KMC initiated immediately after birth on post-randomization mortality during the first 72 h of life and during the neonatal period, compared with continuous KMC initiated after stabilization, in infants with a birth weight of at least 1.0 and less than 1.8 kg born in hospitals in low- to middle-income countries (LMICs). The secondary objectives are to determine the effect of the intervention on time to clinical stabilization, hypothermia, time taken to reach full breastfeeding, hypoglycemia, clinically suspected sepsis, time to hospital discharge, exclusive breastfeeding at the end of the neonatal period, maternal satisfaction with health care in the hospital, and maternal depression at the end of the neonatal period. The nature of the intervention makes blinding not possible.The study is being conducted in five tertiary-level hospitals in low-resource countries of Asia and sub-Saharan Africa, including Ghana, India, Malawi, Nigeria, and Tanzania. These hospitals were selected because they serve as referral centers capable of providing care to women at risk of delivering small babies and have a high proportion of LBW infants. In all of these hospitals, babies with a birth weight of less than 1.8 kg are routinely separated from the mother just after birth and provided care in neonatal intensive care units (NICUs). Care provided in NICUs includes warmth, breast-milk feeding as per availability, and (if required) intravenous fluids, parenteral antibiotics, oxygen, and continuous positive airway pressure (CPAP). There is limited or no access to more sophisticated interventions such as surfactant therapy and mechanical ventilation in most hospitals. Routine KMC is practiced in all of these hospitals and is initiated after achieving stabilization, usually after 3–7 days of age. The quality of care in the participating hospitals has been upgraded though the training of staff on the WHO minimum package of care for small babies. Identical weighing scales, mobile and fixed monitoring equipment, and CPAP equipment have also been provided to all sites, and training in their use was provided by a team of neonatologists.All infants born alive in the participating hospitals with a birth weight from 1.0 to less than 1.8 kg, regardless of their gestational age, are eligible for participation in this trial with their mothers. The mother–infant pair is eligible even if the infants are twins or are born by caesarean section or if the mother experiences some complications during labor and delivery that are expected to be resolved within 3 days.A mother–infant pair is not eligible if any of the following is present: (1) the mother is younger than 15 years of age, (2) the mother (or her guardian if the mother is 15–17 years old) is unable or unwilling to provide consent, (3) the mother is unlikely to be able to provide KMC within the first 3 days after birth , (4) the baby is unable to breathe spontaneously within 1 h of birth, (5) triplets or more, (6) the baby has a congenital malformation that interferes with the intervention or the intervention interferes with the required care for the congenital malformation, (7) the place of residence is not a part of the defined study area (the study area has been defined to make 28-day follow-up home visit feasible), or (8) if for any reason the mother–infant pair cannot be enrolled within 2 h of the birth of the infant.Preliminary unpublished data obtained from the admission and discharge registers of the five selected hospitals show that neonatal mortality among infants with birth weights from 1.0 to less than 1.8 kg was about 32% in 2015. After improved implementation of the WHO-recommended minimum package of care for LBW infants in these hospitals, we expect mortality in the control group to fall by about one third (to be about 21%) during the study period. We calculated the sample size hypothesizing a 20% reduction in mortality  with a power of 90% and a significance level of 5%, allowing a maximum loss to follow-up of 10%. The sample size for comparison of two proportions is 2080 per group; thus, 4200 neonates are required to be enrolled.Promotion and support for continuous SSC initiated as soon as possible after birth: Continuous SSC is initiated immediately after randomization, as soon as feasible after birth, aiming for at least 20 h a day. This is initiated by the mother or the surrogate within the delivery room or the operation theatre or on admission to the NICU and continued during transfer to the NICU and during the stay in the NICU. Mother and infant are kept in the neonatal unit until the infant meets predefined stability criteria. An infant is considered stable when he or she is breathing spontaneously with no oxygen or CPAP support at 40–60 breaths per minute, maintaining oxygen saturation on room air more than 90%, does not have apnea, has a heart rate of 80 to fewer than 180 beats per minute, an axillary temperature of 36.0 to 37.4 °C and does not need intravenous fluids. After stabilization, the mother–infant dyad is shifted from the NICU to the KMC ward, where continuous KMC is provided until discharge from the hospital.Health care for mother and infant provided without separation: The mother and infant are provided health care without separation as much as possible. Mothers are provided a place to sleep, food and health care by obstetric staff while in the NICU. If a mother has any complication for which she needs to be transferred to the obstetric ward or intensive care unit, SSC is continued with a surrogate until the mother becomes available. If the infant requires a procedure or treatment that is not possible in SSC, the infant is shifted to a cot or radiant warmer. SSC is temporarily interrupted for the period of the procedure or treatment and recommenced as soon as possible after that.Promotion and support for early and exclusive breastfeeding: Mothers are encouraged and supported to put the infant to the breast when they are in the NICU. Even if the infant is unable to feed from the breast, putting the infant to the breast provides the infant the opportunity to learn how to attach and suckle. When possible, early expression and feeding of colostrum are carried out. A breastfeeding counsellor is available at all sites to help the mothers solve breastfeeding problems they face.Formative research was conducted in each site to identify barriers to delivering and accepting the intervention and to develop and test solutions to overcome these. In this study, KMC is defined as continuous SSC with the mother or her surrogate aiming for at least 20 h per day, support for exclusive breastfeeding, and required medical care without separation from the mother as much as possible. The surrogate is a female relative or friend identified by the mother to provide SSC when she is unable to do so. Therefore, the intervention consists of three components:Neonates randomly assigned to the control group receive conventional care, and in accordance with the routine at the sites, the mother and infant are separated until the baby is clinically stable. Except for the time of initiation of KMC, all other medical care is the same for intervention and comparison groups. When feeding can be started on the basis of the clinical condition of the baby, expressed breast milk is given using a feeding tube or cup and direct breastfeeding is started when the baby is ready. Short sessions of KMC are started for neonates randomly assigned to the control group when the baby is considered to be recovering  and is at least 24 h old. The mother comes to the NICU to provide these brief sessions of KMC a few times a day during the time allocated for infant feeding. Continuous KMC is initiated for an infant randomly assigned to the comparison group when the infant meets stability criteria for at least a continuous period of 24 h and can be transferred to the KMC ward. As in the intervention group, mother and infant are kept in the neonatal unit until the infant meets the stability criteria. A minimum package of care for the neonates and the mothers is provided as a co-intervention for both the intervention and the control groups.The primary outcomes of this study are mortality between enrollment and 72 h and mortality between enrollment and 28 days of age. Secondary outcomes are presented in Table In addition, deaths from birth to 72 h of age of babies with a birth weight between 1.0 to less than 1.8 kg who are born in the participating hospitals but not enrolled in the study are reported. The schedule of outcome assessments is shown in Fig. A computer-generated block randomization list with variable block size, stratified by site and by birth weight, has been prepared by a WHO statistician. The strata by birth weight are from 1.0 to less than 1.5 kg and from 1.5 to less than 1.8 kg. The random allocation is concealed in serially numbered, opaque, sealed envelopes prepared at the WHO and sent/delivered to the sites.The outcomes are assessed by an independent outcome measurement team which is not involved in the delivery of the intervention. However, the nature of the intervention prevents blinding of outcome assessors as they can observe whether the baby is with or without his or her mother in the NICU. Data analysts will be blinded to the allocation as far as possible.This clinical trial is conducted in compliance with the clinical trial protocol, good clinical practice, and the applicable regulatory requirements. The study is implemented in a standardized manner across all sites, and trial conduct is audited and monitored by quarterly visits by teams from the WHO. Fortnightly teleconferences track progress in the study and help to ensure ongoing harmonization. A full-time site trial coordinator at each site is responsible for the conduct of the trial. Three independent teams at each site are responsible for (i) screening and enrollment, (ii) KMC intervention support, and (iii) outcome measurement. Each team member has been trained in standard operating procedures relevant for their work.An important ethical issue is that mothers will be asked to provide consent for participation when they are in a difficult situation . The nature of the intervention (starting KMC as soon as possible after birth) and the eligibility criteria (birth weight of 1.0 to less than 1.8 kg and no exclusion criteria) mean that the final confirmation of consent needs to be taken in the minutes after birth. The screening and enrollment team therefore “pre-screens” all pregnant women admitted for childbirth (including those who plan to have a caesarian section delivery) if they are not in advanced stages of labor and identifies pregnant women who are at high risk of delivering an LBW infant. Women with a gestational age of less than 37 weeks, intrauterine growth restriction based on second- or third-trimester ultrasound, age of less than 18 years, height of less than 1.50 m, multiple pregnancy, pre-eclampsia or eclampsia, severe anemia, or fundal height of less than 32 cm are identified as “high risk” for delivering an LBW infant. The research assistant approaches such pregnant women, informs them about the study, and invites them to participate in the study. Before taking consent, the treating physician or nurse/midwife is asked to certify that the woman is physically, psychologically, and emotionally fit to provide consent. Additionally, consenting mothers are asked to identify one or two adult women relatives or friends of their choice who could act as their surrogates for providing SSC when and if they are not able to do so. Surrogates have their role in the study explained to them if the mother–infant pair is randomly assigned to the intervention group.Health-care staff and a research assistant weigh every baby born in the hospital; the latter completes a screening form to assess whether the dyad meets all inclusion criteria and does not have any exclusion criteria. If mother and baby are eligible and the mother has consented prior to delivery, her consent is confirmed verbally before she and the infant are enrolled.In situations where an infant is unexpectedly born very small (pre-screening either not carried out or if the pre-screening did not identify the pregnant woman as high risk), consent is obtained within the first 2 h of birth if the treating physician or nurse/midwife certifies that the woman is physically, psychologically, and emotionally fit. The mothers who consent after delivery are given another opportunity to decide about continued participation in the trial 24 h after birth. Mothers who are minors are eligible for enrollment in this study if they are at least 15 years of age and their consent is confirmed by the guardian (parent or husband). Women who undergo cesarean section and have not consented previously are not approached after delivery.Recruitment of an adequate number of participants is ensured by pre-screening every pregnant woman admitted for child birth and screening every newborn born in the hospital. Inclusion of large public referral hospitals in the study and the proposed recruitment period of 2 years aim to ensure that the target sample size is adequately met. The WHO coordination team keeps a close watch on the progress of recruitment through two-weekly teleconferences.The research assistant opens a sealed, opaque envelope with the study identification number, which has the group allocation inside, and records the assignment of the mother–infant pair to intervention or control groups. The research assistant informs the KMC support research assistant about the allocation.If the infant is allocated to the intervention group, the KMC support research assistant who attends all deliveries of potential babies helps the mother (or the surrogate in case the mother is indisposed) to initiate KMC as soon as possible after randomization. Monitoring of oxygen saturation and heart rate is carried out by using a pulse oximeter. The KMC support research assistant also helps to transfer the mother (or surrogate) and the baby to the NICU in SSC. The research assistant continues to support the mother or surrogate to provide continuous KMC after the baby is admitted to the NICU.The infant is kept in SSC as much as possible, preferably with the mother but with a surrogate for the time when the mother cannot provide the intervention. In KMC, the infant is put naked on the mother’s chest. The infant has a cap, diaper, and socks and is secured firmly to the chest with a binder that ensures a patent airway and a shirt that provides containment in the fetal position. All routine care is provided in SSC. Any interruptions in SSC are documented to determine the duration for which the intervention was provided per day. The KMC research assistant also supports the mother in early expression of milk and to help the baby suckle at the breast.If the infant is allocated to the control group, routine care is provided by hospital staff. The infant is transferred to the NICU as soon as possible. When discharged from the delivery room or operation theatre, the mother is transferred to the postnatal ward and the infant remains in the NICU in accordance with current guidelines. When the infant is ready to be fed, the mother provides expressed breast milk. When the infant is recovering, the mother provides brief sessions of KMC in the NICU in accordance with current WHO guidelines.The research team assesses outcomes in the intervention and control groups by using identical methods and procedures. This independent team is not involved with the intervention delivery. Outcome measurement during hospital stay is through review of medical records , interview with mothers, observation of the care given, and assessment of the baby, conducted every 12 h in the NICU and KMC ward. All forms completed by the outcome measurement, screening, and enrollment teams are entered in an electronic platform. Data range and consistency checks are incorporated into the data entry system. Facility-based data collection occurs up to hospital discharge. Several measures are in place to ensure participant retention and complete follow-up. When the mother–infant pair is ready for discharge from the hospital, field assistants accompany mother and baby home to get global positioning system (GPS) coordinates of the house, as well as to confirm contact information and obtain any alternative address where she would like to stay, to facilitate the last follow-up visit. This team builds and retains a strong rapport with the families to know their whereabouts during the follow-up periods. A home visit is conducted on day 29 of age to ascertain outcomes at the end of the neonatal period.For those participants who withdraw from the study, the only data collected after withdrawal consist of in-hospital mortality.Comprehensive monitoring of the safety of the study participants is performed throughout the course of the trial, from enrollment until the day-29 follow-up. Death of an enrolled baby is reported as a serious adverse event, and specific consideration is given for any factor potentially related to intervention. The investigator is responsible for informing the relevant local authorities, institutional review boards, or committees in accordance with their rules and standards. Once a report of an unexpected death is received, the WHO team informs the trial data and safety monitoring board (DSMB) within 24 h of receiving the information, and a final and detailed report is made within 1 week. The DSMB reviews these cases and makes recommendations regarding safety concerns and continuation of the study.Every infant in the NICU is monitored, and information regarding temperature, heart rate, respiratory rate, and oxygen saturation is recorded every 6 h. Blood sugar similarly is monitored every 6 h during the first 24 h after birth and thereafter as and when required. In the KMC ward, infants are evaluated every 12 h up to hospital discharge. If signs of clinical deterioration are seen at any monitoring visit, the diagnosis of possible serious bacterial infection is considered.Unstable mothers or mothers who require special care are not transferred to the NICU. They continue to be managed in the intensive care unit or postnatal ward in accordance with usual hospital practice. The mothers are only transferred to the NICU for providing KMC once they no longer require special care.Obstetric staff is responsible for providing postpartum monitoring and care for all mothers. If a mother is allocated to intervention, she receives routine postnatal care, including medical rounds, examinations, and medication, in the neonatal unit. A minimum care package for mothers is introduced for the postnatal care for mothers in both groups regardless of where they are located. The NICU nursing staff provides support in case of any emergency (such as secondary postpartum hemorrhage) and contacts the obstetric staff to provide definitive care.Health-care staff in the delivery room, neonatal unit, and KMC ward is trained to provide the neonatal care using the minimum care package for both the neonates and the mothers. All relevant staff of the neonatal unit and KMC ward as well as the KMC support research assistants are trained to support KMC for very small infants by the technical support team from Karolinska Institute. This includes how to secure them with the wrap to maintain the baby’s head in a safe position in order to keep the airway open, particularly when the baby is sleeping. All research assistants of the screening and enrollment, KMC support, and outcome measurement teams are also regularly trained in a standardized manual of operations for the study. All research staff is trained in rapport building and communication with mothers and families. Standardization exercises for assessment of clinical signs, including respiratory rate, temperature, chest indrawing, grunting, nasal flaring, and lethargy, have been carried out for all sites to ensure quality of study is maintained.All research team members recruited for the study activities are well qualified and undergo intensive initial training. Their activities are supervised by competent trained study supervisors who support adherence to the manual of operations. The eligibility criteria and the outcomes to be assessed are very clearly defined in the manual of operations and the staff is trained and retrained regularly for that. The infant weighing scale is calibrated daily to minimize measurement errors. Internal quality checks are conducted by the trial coordinators and study principal investigators (PIs) at each site. The two types of quality checks are supervised observations and random independent checks. For the former, each research assistant is accompanied by the trial coordinator/PI for an activity each week. For the latter, 5% of observations are independently checked by the trial coordinator/PI.All participating hospitals are supported to make quality-of-care improvements so they can implement the WHO Essential Care for Small Babies more effectively. The standard of care in accordance with the WHO manual for small infants includes monitoring, thermal control, breast-milk feeding support, and attention to hygiene for all infants. It also includes access to intravenous fluids, antibiotic therapy, and respiratory support with safe oxygen supplementation and bubble CPAP if required.This trial is registered in two trial registries. The trial was first submitted for registration to Clinical Trials Registry - India (CTRI) in December 2017 as the India site was the first to be ready for implementation. It took a few months for clarifications and query resolution, and eventually the trial was retrospectively registered in CTRI (number: CTRI/2018/08/015369) on 17 August 2018. The trial was also registered in Australian New Zealand Clinical Trials Registry (ANZCTR) on 19 November 2018 once all of the African sites were enrolling in the trial (reference number: ACTRN12618001880235).The primary analysis will be executed according to intention to treat. Even if KMC is discontinued because of clinical conditions of the mother or infant, the neonate will not be excluded. Effect size will be estimated with comparison of intervention and comparison group mortality risks. The two primary outcomes are complementary, so adjustment for type I error is not needed. Results will be reported by using Consolidated Standards of Reporting Trials (CONSORT) statement.The flow and number of participants through assessment of eligibility, randomization, follow-up, and analysis are documented Fig. . ReasonsDescriptors for background characteristics in the intervention and control groups will be presented in a baseline table and summarized as means and standard deviations for continuous variables and as frequencies and percentages for categorical variables. These data will represent maternal age, parents’ schooling, family income, household characteristics, mode of delivery, birth weight, Apgar score, and age at randomization. Although our large sample size is likely to yield a balance between the two study arms in the main analyses, we will carefully evaluate the size of any baseline imbalance in our planned subgroup analyses. Imbalanced characteristics that predict death will be appropriately adjusted for statistically.A second analysis comparing quality of care will be performed to ensure that the minimum package of care is offered equally to both intervention and control groups and that the intervention is delivered as planned. These will include time between birth to initiation of KMC and place of care in the delivery room or operating theatre until transfer to the NICU. Additionally, infants’ condition at the time of arrival to the NICU will be compared between groups.P values will be reported. If loss to follow-up for primary outcomes is below 2.5% for mortality, we will calculate RRs and their CIs. If loss to follow-up for primary outcomes is greater than 2.5%, hazard ratios and their CIs will be calculated. If important differences in baseline characteristics between intervention and control groups are identified, multiple logistic regression or Cox proportional hazards models will be used to adjust for confounding.Effect sizes and their 95% CIs will be calculated for the primary outcomes. Significance tests with 5% significance level will be performed, and Subgroup analysis will be conducted for the two mortality outcomes by (1) birth weight categories of 1.0 to less than 1.5 and 1.5 to less than 1.8 kg, (2) gestational age at birth categories of less than 34 weeks and 34 to less than 37 weeks, (3) singleton or twin births, (4) small for gestational age or not, and (5) mode of delivery . Statistical tests of interaction will be used to interpret whether the effect sizes in the categories are different or similar.A secondary analysis stratified by compliance to immediate KMC (iKMC) over 72 h of age will be carried out. This analysis will report on efficacy of the intervention by average duration of SSC, classified as more than 20 h per day, 10–19 h per day, and less than 10 h per day. In this secondary analysis, reverse causality may be an important issue because severely ill newborns may receive less or no SSC. To reduce the possibility of reverse causality, in a sub-analysis we will exclude the babies who show signs of severe illness in the first 6 h of life.The trial steering committee is composed of all PIs from study sites, Karolinska Institute study consultants, and WHO technical staff functioning as its secretariat. This committee is responsible for designing and implementing the study in a harmonized way.An independent DSMB has been established by the WHO. The DSMB includes seven members with expertise in clinical trials, statistics, newborn care, and ethics in resource-limited settings. The DSMB also serves as the technical advisory group for the trial. The DSMB is responsible for safeguarding the interests of trial participants, potential participants, investigators, and sponsors; assessing the safety and early efficacy of the trial’s intervention according to data available at a predefined schedule; monitoring the trial’s overall conduct and quality and protecting its validity and credibility; and making recommendations concerning continuation/termination of study determined by using O’Brien–Fleming stopping boundaries for early benefit/harm or futility. It also serves and advises the WHO and the PIs on the implementation of the trial. The members are independent of the trial and serve in their individual capacity. When about half of the enrollment is completed in the study, the DSMB will review an interim data analysis by arm to determine whether stopping boundaries have been crossed. The study protocol conforms to the SPIRIT checklist  in developing countries. Furthermore, it will provide definitive answers on the impact of iKMC on neonatal mortality and on various outcomes in LBW infants, which will have implications for provision of clinical care. So far, KMC is recommended only for “stable” LBW infants. If the hypothesis is supported, this trial is likely to bring about a global paradigm shift in the intensive care of LBW infants.Inclusion based on birth weight  is considered the best option to select the target population for three main reasons: (1) accurate gestational age estimation is unlikely in study settings where the ascertainment of the date of last menstrual period is generally not accurate and very few women have an ultrasound in early pregnancy, (2) there is high incidence of small-for-gestational-age infants who are also at a high risk of death and could benefit from SSC, and (3) it is relatively easy to have accurate measurement of birth weight.Infants with a birth weight below 1.0 kg have reduced chances of survival even in high-resource settings with sophisticated neonatal intensive care. The intervention would be difficult to implement in infants with extremely LBW. Babies with birth weights of 1.8 kg or more are likely to be stable at or within the first hours after birth and therefore should not be separated from their mothers. They should be provided KMC based on current recommendation.The iKMC trial is unique in several respects. First, it is a pragmatic trial conducted in the real-life scenario of public sector neonatal units in LMICs. The intervention is provided using existing clinical staff in these units, and research nurses are involved only in collection of the research data. Moreover, the trial uses exclusive clinical inclusion criteria and examines important clinical outcomes such as death, sepsis, and breastfeeding rates. The participating centers in the trial were carefully selected to ensure that representation from most of the LMICs and results would be applicable to the vast majority of public sector neonatal units in LMICs.Second, a minimum level of quality of care for the neonates and their mothers is ensured in the trial by implementation and monitoring of the minimum care package in all study hospitals. This includes care and resuscitation at birth, thermal care, provision of CPAP or other adequate and safe respiratory support as needed, breastfeeding support, monitoring, prevention of infections, and management.Third, the trial, while evaluating whether iKMC adds to the benefit of standard KMC for LBW survival, brings about a global paradigm shift of zero separation of mothers from their babies by introducing the concept of mother-neonatal intensive care unit (M-NICU). Continuous KMC for both groups is promoted and supported after they are transferred out of the M-NICU/NICU. This requires a higher level of collaboration between obstetric and neonatal departments.If the trial demonstrates the safety and efficacy of iKMC in LMIC settings with reasonable intensive care facilities, the next logical step would be to scale up the intervention and implement M-NICUs across LMICs. The results from this trial would have implications for high income countries that routinely practice separation of mothers from their babies. Implementation of immediate KMC in these high income countries where newborn mortality is relatively low could improve the quality of non-mortality outcomes such as improved breastfeeding rates, maternal bonding, and long term child development outcomes.The trial is ongoing in all five sites: Ghana, India, Malawi, Nigeria, and Tanzania. The first participant was recruited on 1 December 2017. Participant recruitment is expected to be completed by September 2020. The current protocol is version 3.4, dated 29 March 2018.Additional file 1. SPIRIT  2013 Checklist.


Is parental socioeconomic status associated with telomere length at birth?This cohort study found that early biological aging, reflected by shorter telomere length in newborns, was associated with lower parental socioeconomic status. A higher vulnerability was observed in boys compared with girls.Addressing socioeconomic disadvantages very early in life may improve molecular longevity and overall health for the next generation. Low socioeconomic status is associated with higher all-cause mortality and risks for aging-related diseases. Biological aging is a potential process underlying health conditions related to social disadvantages, which may be present from birth onward.To evaluate the association of parental socioeconomic status with telomere length (TL) at birth, a marker of biological aging.This prospective birth cohort study was conducted among 1504 mother-newborn pairs in Belgium recruited between February 1, 2010, and July 1, 2017.Parental socioeconomic measures, including maternal educational level, occupation, paternal educational level, and neighborhood income based on median annual household income.Mean relative TL was measured in cord blood and placental tissue. By constructing a principal component, an integrative socioeconomic measure was derived that integrates parental socioeconomic status and neighborhood income. Multivariable adjusted regression analyses were performed to associate the integrative socioeconomic measure and TL at birth.P < .001) longer cord blood TL in boys, while no association was observed for girls . The sex-specific socioeconomic status interaction revealed a stronger association in boys compared with newborn girls . In placental tissue, higher socioeconomic status was associated with 1.8%  longer TL in newborn boys but not in girls . For placental tissue, no sex and socioeconomic status interaction on TL was observed .In 1026 newborns , a higher socioeconomic status was associated with longer cord blood TL and placental TL. Each unit increment in the integrative socioeconomic status measure was associated with 2.1% (95% CI, 0.9%-3.4%; This study suggests that parental socioeconomic status is associated with newborn TL, especially in boys. The results indicate that familial social economic factors are associated with the potential cellular longevity of the next generation, with a potential higher transgenerational vulnerability for newborn boys. This cohort study evaluates the association of parental socioeconomic status with telomere length at birth, a marker of biological aging. Studying determinants of TL at birth may lead to a better understanding of the initial TL setting and are essential in understanding their potential role in the developmental origins of health and disease. Maternal perturbations during pregnancy have been associated with newborn TL, including prepregnancy body mass index (BMI),10 air pollution,11 residential proximity to major roads,12 stress,13 and smoking.14Telomere length (TL) is a biological marker of aging. After each cellular division, telomeres shorten; increased oxidative stress and inflammation may accelerate telomere shortening. At birth, TL is highly variable, may be associated with later-life TL, and may be a determinant of an individual’s natural lifespan.15 Meta-analytical evidence suggests an association between SES and adult TL.16 Social disadvantages in early life may induce persistent biological changes.17 In this regard, recent studies, using a limited number of participants, showed associations between newborn TL and maternal educational levels, with potential sex-specific associations.19 However, other large studies of newborns were not able to confirm these associations.21It has been suggested that accelerated cellular or biological aging plays a role in the link between SES and health.22 and in addition, we evaluated whether these associations were different by newborn sex.We hypothesize that parental SES may set the TL of the next generation. We tested our hypothesis in newborns from the ENVIRONAGE  birth cohort,22 For this study, a total of 1504 mother-newborn pairs were recruited from February 1, 2010, to July 1, 2017. The selection criteria included the mother’s ability to fill out questionnaires in Dutch. We achieved an overall participation rate of 61% (1504 of 2465). Selection of eligible mother-newborn pairs is shown in eFigure 1 in the 69 This study was performed according to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline. Written informed consent was obtained from all participants.General study procedures for the ongoing ENVIRONAGE birth cohort have been described previously.23 Maternal and paternal educational level was coded as low, middle, and high  relative to the mean T/S ratio of the entire sample set within each measured batch. The reliability of our assay was assessed by calculating the interclass correlation coefficient of triplicate measures   and proportions of categorical variables (χ2 test) across the different classes of maternal educational levels. An integrative SES variable was constructed by a principal component that combines the different SES measures  using the PROC PRINQUAL procedure in SAS. We used multiple linear regression models to associate the integrative SES variable with cord blood and placental TL. First, we constructed a directed acyclic graph using a priori selected covariates including determinants of newborn and adult TL and variables associated with SES, including parental ages, prepregnancy BMI, maternal smoking, parity, pregnancy complications, cesarean delivery, newborn sex, gestational age, birth weight, and newborn race/ethnicity. Based on the directed acyclic graph, a minimal adjustment model was constructed including maternal age, paternal age, and newborn race/ethnicity, which is required to observe the total association of SES with TL. Second, a full adjustment model was applied, including all aforementioned covariates. All models were adjusted for the variable “batch” to account for the measurement of TL in 2 separate batches. Telomere length at birth differs between boys and girls,11 and the association between SES and TL may be sex-specific.18 Therefore, we formally tested effect modification of newborn sex by adding an interaction term between the integrative SES measure and newborn sex. Newborn sex-specific estimates are reported from these interaction models.All analyses were performed using SAS, version 9.4 (SAS Institute Inc). All Several potential mediators , maternal educational level was correlated with paternal educational level , and neighborhood income was correlated with maternal educational level , maternal occupation , and paternal occupation  , as was maternal occupation  . Girls had 5.2%  longer cord blood telomeres and 5.1%  longer placental telomeres compared with boys.Newborn, maternal, and paternal demographic characteristics by maternal educational classes are provided in P = .047 for interaction). For placenta, no sex and SES interaction on TL was observed . Each unit increment in the integrative SES measure was associated with 1.4%  longer cord blood TL and 1.2%  longer placental TL. For newborn boys, each unit increment was associated with 2.1%  longer cord blood TL and 1.8%  longer placental TL. For newborn girls, each unit increment was associated with a statistically insignificant 0.5%  longer cord blood TL and a statistically insignificant 0.4%  longer placental TL.In unadjusted  and adjuP < .001), with an indirect effect of 0.6% . No mediation was observed for placental TL. Other potential mediators including maternal smoking, exposure to particulate matter with an aerodynamic diameter of 2.5 μm or smaller, birth weight, maternal fruit and vegetable consumption, and maternal physical activity did not fulfill the assumption of a mediator being associated with both exposure and outcome.Prepregnancy BMI partially mediated the association between the integrative SES measure and cord blood TL in the total population. The estimated proportion of mediation was 10.9%  . In boysIn placental tissue, no individual SES measures were associated with TL in the total population . However29 Our results suggest that prenatal SES is associated with TL in boys more explicitly than in girls, which may underlie a potentially higher susceptibility to disease later in life. A potential sex-related heterogeneity at birth may to some extent be in line with observations in adults supporting stronger SES associations in men compared with women, as most studies (18 of 20) indicate that male mortality is more unequal than female mortality across socioeconomic groups.30Our study highlights an important molecular mechanism that may explain the association between parental SES and lifelong health of the next generation. In the ENVIRONAGE birth cohort, we found that SES was associated with TL at birth. We observed a sex-specific association of SES and cord blood TL, with longer TL in boys in association with increased SES. For placental TL, we observed stronger associations in boys compared with girls, but no interaction for newborn sex was observed. Potential differences between cord and placental results may be owing to tissue-specific telomere-regulating differences during in utero development, including differences in telomerase activity, subtelomeric DNA methylation, or telomeric repeat-containing RNA expression.31 including higher risks for preterm births, low birth weight, small size for gestational age, respiratory distress, and increased morbidity and mortality rates, indicating the importance and consequences of a low SES from early life onward.34 In addition to these associations, we found that, on the level of telomere biology, SES is an important factor early in life. In adulthood, SES has been associated with TL; however, at birth results are inconsistent. Our results are in line with the observation that low maternal educational level was associated with shorter cord blood TL in a small population of 54 Latino infants.19 Our findings of a sex-specific association are supported by a recent report that observed an association between maternal educational attainment and cord blood TL in boys.18 In this latter study, annual household income was associated with cord blood TL in boys, which we could not confirm. Sex-specific differences in the association between SES and TL in adults are, however, inconclusive.36 Other studies evaluating cord blood TL9 or infant dried blood spot TL21 did not confirm our findings. However, these studies did not evaluate potential sex-specific associations. Currently, 1 study has reported on paternal educational level, and did not observe an association with cord blood TL.37 Although neighborhood disadvantages have been associated with shorter TL in adults,39 our data do not support an association between neighborhood income and TL at birth. This finding might be explained by the fact that individual SES parameters are of higher importance than surrounding SES measures.Low maternal SES is associated with adverse pregnancy and neonatal outcomes,6 indicating that TL-associated diseases may have their origins very early in life or even at birth. Second, in adults, baseline TL is associated with TL at later stages in life.40 Third, an animal-based study showed an association between early-life TL and lifespan, which may have considerable consequences if that were translatable to humans.7 Furthermore, large population-based studies suggest that a short TL later in life is associated with increased risks for cardiovascular disease and 41 type 2 diabetes42 and with increased mortality.43 Therefore, our results on SES and TL at birth may have important later-life health consequences.Three lines of evidence show the importance of TL in early life. First, TL at birth is associated with later-life TL,44 Low SES may reflect a number of exposures to chronic stress-inducing factors (including factors that lead to increased reactive oxygen species), whereas high SES is associated with exposures to more protective factors that may alter TL.15 Previous studies identified that maternal prepregnancy BMI10 and particulate air pollution exposure11 were associated with TL at birth. In other affluent societies, socioeconomic inequalities in BMI and other associated behavioral and environmental factors have been observed.45 In our study, mothers with low SES had a higher prepregnancy BMI. Formal mediation analysis showed that prepregnancy BMI partially mediated the association between SES and cord blood TL. A moderate mediation of prepregnancy BMI in cord blood but not placental tissue and the lack of explanation by smoking, air pollution, birth weight, and maternal diet and physical activity is in line with studies that observe weak or no mediating effects of these factors on the association of SES and adult or childhood TL.49 This finding may suggest that SES-related psychobiological chronic stress or epigenetic SES-related changes over generations are potentially involved in these associations.51 Although a meta-analysis showed that short-term perceived stress was weakly associated with TL, long-term chronic stress may have a large cumulative effect.52 Therefore, mothers with low SES may have an increased and faster accumulation of allostatic load and TL may represent a cellular memory capturing this cumulative history of oxidative stress and inflammation. These effects are potentially transferred from mother to newborn.53How SES may be associated with TL is unclear. Telomeres are rich in guanine base pairs that are vulnerable to reactive oxygen species, leading to accelerated TL shortening.54 Higher levels of oxidative stress markers and a lower antioxidant capacity have been observed in newborn boys compared with girls.57 In addition, higher estrogen levels during the fetal development of girls may be important in regulating the protective capacity toward oxidative stress.58 Estrogens may scavenge free radicals, regulate antioxidant enzyme expression,59 and enhance telomerase activity,60 and are associated with longer infant TL.61Stronger associations between SES and TL in boys indicate potential stress-compensatory mechanisms or telomere maintenance mechanisms in girls that are absent in boys. Although girls and boys are susceptible to prenatal exposures, the ability to respond to and buffer against prenatal insults may be sex dependent.22This study has several strengths. We have a large (>1000) birth cohort with data on cord blood TL and placental TL. Our integrative SES measure retained its significance as a factor associated with newborn TL beyond numerous potential confounders and in several sensitivity analyses. Our results may be generalizable to affluent populations, as our population is representative for the population at large.9 As both maternal and paternal TL may be associated with their SES, this may mediate the observed association. This mediation could not be tested, as no data on parental TL are available. Third, we could not evaluate paternal occupational status, as no detailed job descriptions were available. Fourth, TL may be associated with childhood SES,63 and therefore parental childhood SES may be associated with our findings. Fifth, we can only speculate on the later-life consequences of TL at birth in association with health and disease, as currently long-term follow-up studies are lacking. Whether TL as measured in this study can causally be linked with later-life diseases is questionable and remains unproven; however, experimental studies show that dysfunctional telomeres can induce cardiomyopathy.64 Prospective follow-up studies are needed to evaluate whether TL at birth represents disease susceptibility later in life.66 Sixth, studying other biological markers of aging,67 including the epigenetic biomarker DNAm PhenoAge,68 could strengthen the evidence of the link between SES and aging. Seventh, other factors during pregnancy, such as hormones, oxidative stress, telomerase activity, and nutrition, warrant further evaluation in the interpretation of our results.This study also has some limitations. First, despite the large population in the study, increasing the population might reveal a more pronounced sex-specific different association for placental TL, which now was confirmed only for cord blood. Second, TL is heritable and parental TL is associated to some extent with newborn TL.Telomere length in early life sets later-life TL. Its potential importance for later-life disease susceptibility underscores the relevance of identifying early-life determinants of TL. Our results show a potential sex-specific association between parental SES and TL at birth, indicating a potential higher susceptibility in boys with a low SES at birth. Socioeconomic disadvantages in prenatal life may have potential lasting implications for molecular longevity or cellular aging.


Eutherian mammals have characteristic lengths of gestation that are key for reproductive success, but relatively little is known about the processes that determine the timing of parturition, the process of birth, and how they are coordinated with fetal developmental programs. This issue remains one of biology's great unsolved mysteries and has significant clinical relevance because preterm birth is the leading cause of infant and under 5 year old child mortality worldwide. Here, we consider the evolutionary influences and potential signaling mechanisms that maintain or end pregnancy in eutherian mammals and use this knowledge to formulate general theoretical evolutionary models. These models can be tested through evolutionary species comparisons, studies of experimental manipulation of gestation period and birth timing, and human clinical studies. Understanding how gestation time and parturition are determined will shed light on this fundamental biological process and improve human health through the development of therapies to prevent preterm birth. This tiThe observation that the peak of birth timing in women coincides with the trough of neonatal mortality suggests that developmental and physiological mechanisms that optimize the timing of parturition have likely been under strong selection through evolution. Similarly, genetic polymorphisms in mothers and newborns that contribute to optimization of parturition timing may too be under the influence of selection. Of course, the optimal time for birth is also influenced by an organism’s life history and ecology, such as litter size, maternal habitus, circadian and seasonal activity patterns, and social and environmental exposures, all of which vary widely across mammals. Therefore, it is not surprising that much diversity exists in the physiology of pregnancy and birth timing among mammals. This is evidenced by the observation that genes associated with reproduction exhibit high levels of sequence divergence among eutherian mammals, similar to those associated with adaptive immune system development and function .Homo lineage. This lineage specificity would explain why cross-species observations, although revealing some principles of birth timing, have not significantly advanced understanding of human birth timing. One reason for this evolutionary divergence in strategies between humans and other species may be the unique increase in brain size in humans, even in comparison to other primates, over the last few million years and the physical or metabolic constraints encountered because of it  may override pregnancy maintenance signals to provide fail-safe mechanisms that serve the survival interests of the mother  and the fetus/neonate ;each mammalian species has evolved its own strategy for parturition timing, which may or may not be conserved in other species. Compared to other organs or systems, reproductive organs (e.g. uterus and placenta) are more recently evolved; new functions or novel cell types in these organs are thought to have evolved from existing tissues by rewiring existing genetic regulatory networks; pregnancy-associated traits, including parturition, evolved ‘on’ pre-existing cardiovascular, metabolic, and immune systems, and the reproductive strategy coordinates with these systems . At the pregnancy-associated traits, including parturition, are influenced by both maternal and fetal genomes and parental environmental effects . The invThe core principles listed above are shared across eutherian mammals due, in part, to the ancestral evolution of viviparity—to understand the evolution and diversity of parturition we must uncover the evolutionary substrate upon which it was formed. The hallmark traits of eutherian viviparity are: (1) retention and gestation of the fertilized egg(s) in the female reproductive tract (uterus); (2) development of a placenta that facilitates the transfer of oxygen and nutrients from the maternal compartment to the conceptus, and (3) delivery of the fetus and its placenta via the process of parturition at a specific stage of gestation. Each trait is critical for the success of viviparity, and therefore has likely been under strong selective pressure to optimize reproductive fitness . The couPhylogenetic analyses suggest that viviparity originated from oviparity  in at least 150 lineages, including in mammals, fish, and reptiles . The evoParturition, and especially its timing, is a mission-critical event for the success of mammalian viviparity. Normal parturition occurs at a specific time referred to as term, when the fetus is sufficiently mature to survive as a neonate, and the mother is able to provide care for the neonate’s nutrition, protection and physiologic stability, while preserving her own fitness. Timing mechanisms for parturition have likely been selected to optimize reproductive fitness based on benefits to the mother and fetus for the current pregnancy, and benefits to the mother’s survival and future reproductive potential . One important general association with birth timing is its correlation with body size at birth . This asStudies utilizing concordance in birth timing in offspring of twins, or family-based segregation or epidemiology, suggest that 30–40% of the variation in human birth timing is due to genetic factors, and these reside largely in the maternal genome . The ‘coDo species other than humans exhibit a significant frequency of preterm birth? This question is difficult to answer since preterm birth in humans is an arbitrary definition. If we simply scale the assignment of preterm birth based upon duration of term gestation  then other eutherian mammals also experience preterm birth . FrustraPregnancy is the physiologic state in eutherian mammals in which a fertilized egg is retained and gestated in the cavity of the uterus. For pregnancy to be maintained, the smooth muscle of the uterine wall (the myometrium) remains relaxed, quiescent, and grows and distends to accommodate growing conceptus, whereas the uterine cervix remains rigid and closed. In addition, maternal physiology adapts to provide nutrients and oxygen to the developing fetus. Remarkably, a conserved trait in all viviparous mammals examined so far is that the establishment and maintenance of pregnancy are dependent on the steroid hormone progesterone (P4) . As its 2α) produced by the uterine endometrium acting on its receptors on cells in the CL. Thus, term parturition in rodents is induced by PGF2α production in the endometrium. In other species, such as sheep and primates, the source of P4 for pregnancy maintenance shifts from the CL to the placenta  of the ovary. Some species, such as rodents, maintain ovarian P4 production as the sole source of P4 to maintain pregnancy, and parturition is initiated by loss of P4 due to CL regression . In rodeplacenta . In humaplacenta . In sheeplacenta . This, hplacenta . Nonetheplacenta . One expplacenta  and alteplacenta .The control of human birth timing remains enigmatic, largely because of our limited ability to precisely predict its occurrence based upon absolute days of gestation. In contrast, the timing of birth in other species, exemplified by sheep and mice, is predictable and the underlying regulatory signals have been defined. For example, pioneering studies by PTGS1, which subsequently generates prostaglandin F2α –one encoded by ndin F2α . PGF2α fndin F2α .Cortisol plays a key role in promoting fetal organ maturation in humans, however, parturition in women is not initiated by fetal HPA activity. Although the work of Liggins and colleagues in sheep was groundbreaking for understanding hormonal pathways that may promote parturition, the specific pathways operating in the sheep do not appear to operate in the same way in women . The ancGJA1 that encodes connexin-43 a major subunit of intracellular tight gap junctions that facilitate contractile synchrony between myometrial cells, and OXTR that encodes the oxytocin receptor and increases myometrial sensitivity of the uterotonic actions of oxytocin., PTGFR encodes the prostaglandin FP receptor and PTGS2 that encodes cyclooxygenase-2 (COX-2) and generates critical parturition proinflammatory prostanoids, such as PGE2 and PGF2alpha, that induce cytokines such as interleukin-1 that are also pro-labor  that are also steroid hormones derived from cholesterol, whose abundance increases at the end of gestation in most species and act to augment uterine contraction by inducing the expression of genes in uterine smooth muscle cells encoding factors that increase contractility and excitability. For example, in the rat and mouse estradiol induces the expression in myometrial cells of ro-labor .Uterine tissue-level inflammation is associated with normal term parturition across mammals. However, less clear is whether proinflammatory signals are involved in the parturition initiation process from those species that do not undergo luteolysis and systemic progesterone withdrawal or act to facilitate or accelerate the process once initiated. In primates, the inflammatory cascade is apparent but may come after the proximal initiator of parturition . For exaWhile the leading cause of perinatal death is preterm birth, postterm birth  also places the newborn at higher risk for perinatal mortality and neonatal acute and long-term adverse health effects . ViewingADAMTS13 gene, also known as von Willebrand factor-cleaving protease, that is involved in blood clotting  axis late in pregnancy. Importantly, the cortisol also stimulates functional maturation of fetal organ systems, especially the lungs, gastrointestinal tract and liver, thus ensuring the newborn lamb is equipped for life outside the uterus. However, studies in multiple species show that although the effect of fetal cortisol to promote organ system maturation appears to be conserved across species , its role as a driver of parturition is not conserved .Retention of the conceptus in the uterus is a hallmark trait of eutherian mammals and requires that the uterine tissues accept and accommodate the developing conceptus for the gestation time needed to complete the fetal development program. The parturition block model posits that a blocking agent or system dominates for most of pregnancy to actively prevent parturition, and that labor and delivery ensue when the block is removed. This implies that if not for the block, the uterus would expel its contents. Interestingly, uterine emptying is not limited to parturition. Large uterine fibroids can be spontaneously expelled through a process that includes myometrial contraction and dilation of the cervix . In caseExistence of a parturition block was first recognized in the late 1800s from observation that pregnancy in rabbits is dependent on a factor secreted from the maternal corpus luteum and that removal of the CL initiated parturition at all stages of pregnancy. The pro-gestation parturition blocking factor was eventually identified to be Δ5-keto-steroid and named progesterone (P4) . StudiesThe P4 block model posits that birth timing is determined by factors that induce actual or functional P4 withdrawal. P4 is thought to maintain pregnancy by exerting anti-inflammatory effects on the uterine tissues, thus preventing inflammation-associated uterine emptying. In this scenario, the gravid uterus is poised and prepared for parturition throughout pregnancy but is restrained by an anti-inflammatory P4 block. Diversity exists in upstream signals to induce withdrawal of the P4 block. The P4 block to labor may diminish with advancing gestation under the control of a clock mechanism until a threshold is reached below which the parturition cascade is initiated. The system may function in a stochastic manner – the probability of parturition increases with gradual decline of the P4 block. It is also possible that multiple up-stream signals for parturition converge to induce P4 withdrawal.In most eutherian mammals, parturition is associated with a systemic decrease in maternal P4 levels due to regression of the CL or the induction of enzymatic activity in placental cells that mitigates P4 secretion. This, however, does not occur in humans and other anthropoid primates; instead, parturition occurs with the uterine tissues exposed to high levels of P4 . The sugThe parturition block model reflects the balance between maternal and fetal/paternal genetic interests in the pregnancy condition. Natural selection would favor a conceptus that can maintain pregnancy and extract resources form the mother for the longest amount of time. Studies of imprinted genes suggest that this trait is in part conferred by paternally imprinted genes. In contrast, the interests of the mother include surviving the current pregnancy and maintaining her reproductive competence for future pregnancies and caring for current dependent offspring. In this context, it would be logical that a parturition block signal would be coming from the fetus. However, the block cannot be absolute and would need to be counterbalanced by maternal signal(s) to stimulate parturition when maternal interests and/or fetal viability are compromised. Thus, a fetal-based parturition block would be expected to eventually diminish and/or be overcome by a maternal-based parturition stimulator signal. Indeed, a conserved trait in eutherian mammalian species is that parturition is promoted by withdrawal of the P4-block to labor, suggesting that the stimulatory signal(s) for parturition converge on nullifying the P4 block.This model posits that the labor state is actively induced by acute or gradually accumulating signals. The signals may be linked to the size of the conceptus and the amount of uterine wall and cervical distention , stressoThis model posits that a combination of restraining and promoting signals leads to parturition when a crossover threshold is reached for dominant labor-promoting actions, as suggested in a more specific manner for the relationship of P4 and inflammation signals . This moThe importance of birth timing on species-level reproductive efficiency would have favored multiple signals for parturition depending on lineage-specific selective pressure. In this scenario natural selection would favor mechanisms promoting robustness and phenotypic stability that would include buffering by genetic networks, epigenetic canalization, and complementary, partially overlapping or redundant actions across pathways or genes as described for other developmental systems . In geneCan the four proposed models be experimentally distinguished? A useful starting exercise is to determine if existing data refute one or more of the models. Significant divergence in mechanisms may exist across species, so whether one species follows a specific model cannot be completely understood by findings in another. For example, one clear piece of evidence that argues against the Fixed Maternal Clock Model comes from examining the timing of birth in cross-species hybrids. Matings between female horses and male donkeys produce mules. Under the Fixed Maternal Clock Model, the time to birth in such pregnancies would be expected to reflect the mother’s clock. However, mules are delivered on average between (11.4 months) when a horse (11.2 months) and donkey (12 months) would normally deliver , consistIn sheep, fetal hypothalamic-pituitary-adrenal axis activation is essential for parturition and may suggest a fetal fixed clock. However, fetal adrenal activation may still be downstream of the true parturition initiating signal and represent a downstream effector pathway. Rodent pseudopregnancy, the state which arises when receptive females are mated to sterile males, lasts approximately one-half the duration of a normal, fetus-containing pregnancy . This suA classic physiological approach to dissecting stimulatory or inhibitory signals influencing a phenotype, such as in our Models 2–4, is to perform cross-circulation, or parabiosis, experiments. These experiments link the circulations of two animals to allow circulating factors to be shared between them. As applied to rat gestation and parturition, studies have been performed which revealed the ability of a gravid female 2 or 3 days earlier in gestation (i.e. mated later) to delay the onset of birth in the gravid female that had been impregnated earlier . InteresThe above methods for testing the proposed models for parturition initiation, provide interesting and useful information, although each has its own limitations. We propose that applying an evolutionary, comparative framework will complement these methods, together leading to otherwise unobtainable insights. It is generally accepted that the initiator of mammalian parturition must be under strong selective pressure to optimize reproductive fitness . Indeed,Evolutionary approaches that collect, curate, and compare the same pregnancy-related data across species promise to be particularly informative, especially to shed light into the innovations leading to possibly the re-wiring of regulatory network of preexisting genes not previously involved in parturition into pregnancy regulation. The reproductive strategy differences and consequences of ecologic niche and environmental exposures will further inform the mechanisms that prompt birth. We return to principal proposed by the Danish physiologist Acomys carihinus), Mongolian gerbil (Meriones unguiculatus), and house mouse (Mus musculus) have evolutionary divergence times from one another of 18–24 million years (Considering these potential animals of choice in an evolutionary framework promises to be particularly revealing. We will provide one example in the Muridae family that could be explored. The spiny mouse (on years . Remarkaon years , while hon years  and Mongon years  have geshttps://www.ncbi.nlm.nih.gov/nuccore/PVKX00000000.1, https://genome.ucsc.edu/cgi-bin/hgGateway, In WNT4 gene region shown to be involved in the regulation of gestational duration in mothers has been identified to mechanistically contribute to birth timing by establishing a new high affinity estrogen receptor binding site (The ‘animal of choice’ evolutionary approach combined with recent evidence from human genome-wide association studies may reveal shared pathways, gene networks, transcription factors, and regulatory elements controlling human pregnancy and parturition. The initial gestation length loci identified by GWAS in the human maternal genome suggest critical roles of the decidua, the maternal interface with the developing placenta and fetus, and estrogen signaling in decidual cells . For exaing site . Is the ing site  and the ing site  provide ing site .The determinant of birth timing is a critical and exciting big question that awaits elucidation. Situated at the intersection of biology, environment, and social context, including race and racism, preterm birth poses challenges that we must address. Are there other general models and frameworks for solving the enigma of birth timing? For example, an alternative framework and set of models would focus on the source of parturition initiation: maternal, fetal, interactive maternal-fetal, environmental, etc. The community of biomedical scientists interested in this area of investigation are encouraged to comment on this article with their ideas, constructively challenge one another, and us, and work to solve the problem. Further, one intent of this dialogue is to bring new voices and ideas into the discussion. We hope to stimulate the vision and curiosity of diverse investigators to gain new insights and answer this important question.


Maternal health and nutritional status before and during gestation may affect neonates' immune system and energy balance as they develop. The objective of this study was to associate certain clinical markers of maternal adiposity  and neonatal adiposity  with the levels of pro- and anti-inflammatory cytokines in umbilical cord blood at birth: IL-1β, IL-1Rα, IL-4, IL-6, IL-10, IFN-γ, and TNF-α. An exploratory cross-sectional study was conducted with a convenience sample of women from one hospital recruited shortly before giving birth through scheduled cesarean section. Of 31 the pregnant women who agreed to participate and met the inclusion criteria, twenty-nine newborns from these women were analyzed. Three cases of tobacco smoking during pregnancy were identified as an unexpected maternal risk factor and were included in the analysis. Typical of the population treated at this hospital, ten of our participants had diabetes during pregnancy, and nine of them had a pre-pregnancy BMI> 25. Non-parametric statistical analyses and a generalized linear model with gamma scale response with a log link were performed. Results: Correlation analyses, differences in medians, and a prediction model all showed positive and significant results between cytokine levels in cord blood and neonatal abdominal circumference, birth weight, and waist-height index. For maternal variables, smoking during pregnancy showed significant associations with cytokine levels in cord blood. Conclusion: This study found a variety of associations suggesting that increased neonatal adiposity increases pro-inflammatory cytokine levels at birth. Cytokines can act as hormones in the immune system and are generally influenced by nutritional status in the same way that other physiological systems would be .Neonatal cytokines levels may be good indicators of future health status. There is a compelling rationale for measuring neonatal cytokines, as there is a paucity of investigation on using neonatal cytokine levels as indicators.Maternal nutritional status is one of the most dominant contributors to a fetal environment that potentially modifies a newborn's physiology –4. ObesiVery little, if any, is known about the impact that fetal overnutrition  has on the immune system of newborns. Ninety percent of body fat at birth is deposited in the last ten weeks of gestation, and maternal concentrations of circulating free fatty acids regulate the provision of lipids to the fetus , 10. FreNeonates with higher fat mass could have prenatal increased exposure to FFAs , 15. FatThis article reports the analysis of an exploratory study conducted with twenty-nine mother/child binomials on the associations between pre-pregnancy body mass index (P-BMI), gestational weight gain GWG), neonatal abdominal circumference (AC), waist/height index, and weight at birth on the levels of seven cytokines in the umbilical cord blood at birth. As secondary results, information on another risk factor—exposure to tobacco smoking—was also gathered and associated with the same cytokines.In this exploratory cross-sectional study, we examined possible associations between neonatal cytokines and maternal and neonatal adiposity clinical markers that may influence fetal development. This project was carried out between February and June of 2017 at the Instituto Nacional de Perinatologia in Mexico City after being approved by the relevant Investigation Committee, Research Ethics Committee, and Biosafety Committee (registration number 384-212250-22651).Inclusion criteria were: being a pregnant woman over the age of 18 years, carrying a singleton pregnancy, being scheduled for an elective cesarean section, and not yet having gone into labor. Only women with a scheduled cesarean section and who had not yet gone into labor were included in the study to control for the inflammatory influence of labor and vaginal delivery. Exclusion criteria included: the use of any antimicrobials or steroids in the previous four weeks or a diagnosis of any health condition known to influence maternal/neonatal cytokine levels .A convenience sample of eligible patients was recruited in a consecutive fashion in the hospital's labor and delivery room shortly before giving birth by scheduled cesarean section. There, the study was explained to them, and they signed informed consent—in the presence of two witnesses who also signed the same document—for the collection of clinical data and biological material. Maternal and neonatal clinical/sociodemographic data, obstetric outcomes, and behavioral habits were retrieved from medical records and recorded .The study initially commenced with 31 participants, but two were excluded because their maternal venous blood sample was obtained after a cesarean section. Taking a sample after a cesarean—because of surgical manipulation and the administration of drugs and/or anesthetics—is known to modify the parameters of the cytokines in newborns.2 [All participants were asked to report their pre-pregnancy weight and height. Self-reported pre-pregnancy weight and height are useful and reliable proxies due to their adequate correlation with real measurements . With th2 . Women's2 . GestatiThe Mexican population has a high prevalence of obesity and overweight , and an estimated diabetes mellitus prevalence of 11% ; gestatiNeonatal weight (g), length (cm), and abdominal, thoracic, and head circumferences (cm) were obtained at birth by trained pediatricians using the Lohman technique . A SECA-Maternal blood and neonatal arterial cord blood using a Bio-Plex Pro Human 27-plex assay according to the manufacturer's instructions . Samples were processed in a Bio-Plex System, BioRad.We selected seven cytokines  to be representative of pro-inflammatory and anti-inflammatory cytokine groups.Results were analyzed using the IBM SPSS Statistics for Windows, Version 23.0 . Data in tables are presented as median and interquartile range. Correlations between neonatal cytokines and maternal and newborn nutritional status were assessed using the Spearman correlation coefficient. Differences in somatometry at birth between the P-BMI and maternal diabetes groups were evaluated with the Kruskal-Wallis test. Differences in neonatal cytokines levels between groups were compared with a Mann-Whitney U. The CRT (classification decision trees) method of the CART model was used to identify the cut-off points of the maternal and neonatal variables that showed significance in the Mann-Whitney U analysis. Significant results were defined as those with a probability of α-error < 0.05.The gamma scale response with log link regression of the Generalized Linear Model was performed to assess the independent effect of maternal clinical adiposity measures (P-BMI and GWG), and clinical adiposity measures  on umbilical cord blood cytokines levels.Due to the small sample size, a post hoc power calculation was carried out after data collection, using the G*Power analytical program. A β value was calculated with an exact post-hoc test for bivariate correlation for non-parametric differences between groups.All women were Mexican, from a middle or middle/low socioeconomic background, and had no access to other formal healthcare service services. Nine women with diabetes  had overweight or obesity and one normal-weight woman had pre-existing diabetes mellitus. As these comorbidities are endemic and uncontrolled in our population, it places us in the position of studying the effect that these morbidities can have on newborns. Three pregnant women smoked during gestation .All neonates presented an Apgar score of 8 and 9 at 1:00 and 5:00 minutes, respectively, and were born healthy (pediatrician's diagnosis). Fifteen newborns were girls, and fourteen were boys. The neonates were born with an adequate weight for their gestational age.There were no statistically significant differences between children born to mothers with normal, overweight, and obese P-BMIs in any of their anthropometric values, including birth weight (p = 0.7), length (p = 0.9), waist/height index (p = 0.8), and abdominal circumferences (p = 0.9). Similarly, no significant difference was found when comparing children born to a diabetic mother with P-BMI ≥ 25 and diabetes (n = 9), against those born to a non-diabetic mother with a P-BMI ≥ 25 (n = 8), to a non-diabetic mother with P-BMI <25 (n = 11), or to a diabetic mother with P-BMI<25 (n = 1): weight (p = 0.5), length (p = 0.9), waist/height index (p = 0.3), and abdominal circumferences (p = 0.4).The original intention of this exploratory study was to establish the convenience of doing a large comparative study. In this sense, the results obtained were encouraging, as they were statistically significant and supported by moderate and high statistical powers.The influence of the mother's P-BMI and GWG on the pro-inflammatory state of her infant at birth had been previously studied, notably by Dosch et al., who found higher values of PCR and TNF-α in cord blood in pregnancies complicated by obesity .Like us, Vega and Estampador , 26 repoFor newborns, it has been documented that being born to an overweight or obese mother or one wiAbdominal circumference, birth weight, and waist/height index are good clinical markers of adiposity in newborns –32. AbdoCurrent evidence suggests that maternal lipids  from obese, glucose-tolerant women are contributing to excess fetal fat deposition starting from the first half of pregnancy , 34. In The generalized linear model confirmed a pro-inflammatory predictive pattern in umbilical cord blood associated with the abdominal circumference at birth. These results lead us to posit that AC at birth, and other markers of neonatal adiposity, influences the immunological state at birth, probably more than maternal fat mass. Other authors have also found an association between increased fetal growth and inflammatory cytokines, such as IL-6 and TNF-α . An inteThe inflammatory state we observed in this sample of newborns may not have been exclusively mother-induced, and it is entirely possible that it was produced by an immune response from the newborn's own increased adipose tissue. This is certainly an area to further speculate on and to study. Numerous statistical and epidemiological observations show direct correlations between adult obesity with childhood and neonatal obesity, and the association between the distribution of body fat in young children and metabolic and cardiovascular risk later in life –41.An unexpected finding in this study was the three cases of smoking during pregnancy; this small sample provided significant associations in the statistical analysis. We observed that the three cases of maternal tobacco use during pregnancy were able to predict the elevation of levels of the neonatal cytokines IL-1β, IL-1R α, IFN-γ, and TNF-α. Infants of smokers also had higher levels of cytokines IL-1β, IL-1R α. In contrast with our results, Almanzar found no differences in cytokine levels among the newborns of smoking mothers versus non-smoking mothers . This diIn this study, there were no differences in cytokine levels between infants of mothers with diabetes and infants of mothers without diabetes. This is undoubtedly an important area of research that requires a larger sample size to draw conclusions.Clinical variables related to fat mass in neonates were associated with higher levels of pro-inflammatory cytokines at birth, with abdominal circumference being the most significant outcome. Our study was unable to conclusively establish associations between maternal clinical fat and pro- and anti-inflammatory cytokine levels in cord blood. More studies are needed to benchmark average values of cytokines at birth and the changes that cytokines undergo due to environmental and maternal health conditions as part of the fetal programming process.Due to the salient ethical considerations of studying human newborns, neonatal cytokine levels is a little-studied topic, and we performed this pilot study as we could not find reliable reference values to calculate the variability of cytokines as birth. The initial intention of this project was to evaluate the convenience of performing a larger comparative study. In this sense, our results are encouraging, as our principal results were statistically significant and supported with moderate and high statistical powers. We hope that this study may be an approach to understanding how neonatal adiposity can be associated with newborns' cytokines and that these can be an area of future research.


We report the first observations of periodic oscillations of an atmospheric electric field simultaneously derived by field mills at four observation sites at a distance of 50–65 km in metropolitan Tokyo. Oscillations were detected during a snowfall event on 23–24 November, 2016. The main period of the oscillations of the atmospheric electric field at CHB was 78 min, which was similar to those at other sites. The periods of 39.0, 54.6, and 78.0 min observed at Chiba (CHB) were similar to those observed by W-band cloud radar (FALCON-I) reflectivity below a height of 5 km. High coherence of the 78-min period between the atmospheric electric field at CHB and the X-band phased array weather radar reflectivity suggest that the periodic oscillations of the atmospheric electric field during snowfall were caused by vertically convective cells in snow clouds with a radius of 60 km centered on CHB. The pattern of the oscillation was clear sinusoidal waves, and the oscillation was observed at Kew Observatory, England, on 26 February, 1946. Traditionally, the atmospheric electric field is defined as positive (negative) when it is downward (upward) from the ionosphere to the Earth surface. During periodic oscillations of the atmospheric electric field during snowfall events, when the atmospheric electric field is positive or negative, the polarity of snowfall particles measured at the ground is negative or positive, respectively. The relationship between the two polarities of the atmospheric electric field and rain or snow particles at the ground is called “mirror image relation” or “inverse relation”4. Previous studies compared the atmospheric electric field with the polarity and number density of snow/rain particles on the ground using thermionic electrometers2. Most periodic oscillations of the atmospheric electric field occurred during snowfall from nimbostratus clouds5, which are typical rain or snow clouds that are widely spread and close to the ground. A wave pattern of the atmospheric electric field, with periods of 10–30 min, during snowfall in Hokkaido, Japan, was revealed from cumulonimbus clouds6. Oscillations of the atmospheric electric field with periods of about 20 min and inverse relation were also observed in Hokkaido, Japan, during snowfall on 16 January, 19787. In seven out of eight oscillation events during snowfall in Japan, graupel particles were charged positively, and the surface of the graupel particles was dry. A number of small snow particles were present with the graupel particles. The mirror image relation was not always observed at heights of 100–200 m, although it was always observed at 0–22 m (where 22 m corresponded to the building rooftop), based on balloon observations8. At a cloud height of 100–200 m, the charge strength and polarity of snow particles were weak and positive, respectively, although they were intense and negative near the ground, suggesting that snow particles became negatively charged while falling to the ground. The previous studies proposed a mechanism in which the atmospheric electric field at ground level was affected by ions due to corona discharges8. These studies revealed a relationship between oscillations of the atmospheric electric field and the polarity of snow/rain particles, based on observations obtained with Bendorf and thermionic electrometers. However, the studies did not investigate the internal structure of snow clouds during the oscillations, nor the variation in the electric field. Moreover, the following questions remain: why did the atmospheric electric field oscillate during snowfall, and what underlies the long period of the oscillations, of several tens of minutes?An atmospheric electric field or potential gradient oscillation observed at ground level with long periods (60 ~ 80 min) during sleet and snowfall events without wind turbulence was first reported10. This study investigated the relationship between oscillations in the atmospheric electric field and snow clouds. In this study, we investigate periodic oscillations of the atmospheric electric field during a snowfall event on 23–24 November, 2016, using a field mill and 95-GHz cloud radar, FMCW radar for cloud observations (FALCON-I). FALCON-I is a cloud radar with high spatial and sampling resolution developed at Chiba University, Japan11. This study first reports the relationship between long oscillations of the atmospheric electric field and temporal variation in the internal microstructure of snow clouds using FALCON-I. The periodic oscillations of the atmospheric electric field during this event did not apply to the EOSO, because thunderstorms did not occur.End-of-storm oscillations (EOSO) below thunderstorms in the dissipating stage are associated with long-period  oscillations of the atmospheric electric fieldSnowfall occurred due to an intense cold air mass and low atmospheric pressure in the Tokyo metropolitan area from 15:00 UT on 23 November to 07:00 UT on 24 November, 2016. The accumulation of snow in November was the first observation ever in both Tokyo and Chiba (CHB), and the snowfall was the first in Tokyo in 54 years. On 24 November, 2016, the maximum accumulation of wet snow at CHB was 2 cm according to the Japan Meteorology Agency (JMA).The locations of field mills at Chiba University , Kakioka, Ibaraki , Koganei, Tokyo , and Musashino, Tokyo ; the FALCON-I at CHB; and a X-band phased array weather radar (PAWR) operated by Japan Radio Co., Ltd. , Japan are shown  at the four sites during snowfall is shown Fig. . The arr14. The intense period also started at a height of 800 m at 13:00 UT, and gradually fell to a height of 300 m at 18:00 UT on 23 November, 2016, corresponding to a bright band15. The bright band is a radar signature of the layer in which snow transitions to rain. Such detailed internal structures of the snow cloud could be seen by the FALCON-I . Another factor may be differences in location among the snow clouds. FALCON-I monitors clouds overhead with a narrow beam 11, which is about ~ 100 m from the location of the PAWR data. The bright band was observed at heights of 0.5–1.0 km between 15:00 UT and 17:00 UT, which was consistent with the FALCON-I reflectivity  did not occur due to the slow speed of the wet snow, although the snow particles might move horizontally.Variation in the atmospheric electric field, vertical Doppler velocity for each height observed by FALCON-I, and a typical radar Doppler profile map at 23:00 UT on 23 December, 2016, during the snowfall event is shown Fig. . The dirA periodogram of the atmospheric electric field at CHB, and the period of the FALCON-I radar reflectivity for each height based on FFT, are shown Fig. . The maiThe coherence between the atmospheric electric fields at CHB and KAK peaked at 0.82 after 73.1 min. The coherence calculation is described in the Methods. The maximum coherence values of the atmospheric electric fields for CHB-KGN, CHB-MSN, KAK-KGN, KAK-MSN, and MSN-KGN were calculated to be 0.62 (period 51.2 min), 0.45 (113.8 min), 0.58 (53.9 min), 0.52 (64.0 min), and 0.99 (78.8 min), respectively. These coherence values were all significant at the 95% confidence level. The coherence values were particularly high at 73.1 and 78.8 min. Only the coherence of the 78-min period between the atmospheric electric field at CHB and FALCON-I radar reflectivity was significantly large below a height of 3 km  North–South and (b) East–West directions, centered at CHB , which was determined by comparing the values observed inside the room to those on the ground outside, and used as the reference for two observation systems.The atmospheric electric field has been observed with an EFM-100 field mill (Boltek) on the roof of a building on the campus of Chiba University, Japan, since 1 June, 2016. The dynamic voltage range is ± 20 kV/m with a 0.5-s sampling time. The cut-off frequency of the low-pass filter is 11 Hz. Field mills made by Boltek Corporation were also used at KGN and MSS. We discuss the variation in the atmospheric electric field, because the three field mills at CHB, KGN, and MSS have not been calibrated. At KAK, the atmospheric electric field has been observed using a water dropper inside the observatoryThe 95-GHz (W-band) cloud radar, FALCON-I, was originally developed by our research group at Chiba University, Japan. FALCON-I is shown Fig. ; it consWe also used a PAWR developed by Japan Radio, for which the transmitted frequency is 9.4 GHz. The PAWR can observe the radar reflectivity of cloud/rain particles and radial Doppler velocity every 30 s with a grid spacing of 75 m and a radius of 80 km at heights of up to 15 km. The PAWR can cover the FALCON-I location, since the distance between them is 16.2 km. The atmospheric electric field, FALCON-I, and PAWR data are provided in the Supplementary Information.coh(ω), is defined by the following formula:ω is the angular frequency; Sxy(ω) is the cross-spectra of two discrete time signals; Sxx(ω) and Syy(ω) are the spectra of x(t) and y(t), respectively; and Kxy(ω) and Qxy(ω) are co- and quad-spectra, respectively19. Here, x(t) and y(t) denote the variation in the atmospheric electric field between two observation sites, or the variation in the atmospheric electric field and radar reflectivity for each height, respectively.Coherence, xy (ω) and Qxy (ω) are the real and imaginary parts of Sxy (ω), respectively, and are calculated as follows:KThe phase difference, Supplementary Information 1.Supplementary Information 2.Supplementary Information 3.Supplementary Information 4.Supplementary Information 5.Supplementary Information 6.Supplementary Information 7.Supplementary Information 8.