Primary exposures were maternal delivery intact PTH (iPTH) or whole PTH (wPTH) and outcomes were gestational age- and sex-standardized z-scores for birth length (LAZ), weight (WAZ), and head circumference (HCAZ). Hypothesized regulators of PTH included calcium and protein intake, vitamin D, magnesium, fibroblast-like growth factor-23 (FGF23), and C-reactive protein. Maternal iPTH was not associated with birth size in linear regression analyses; however, in path analysis models, every SD increase in log(iPTH) was associated with 0.08SD  higher LAZ. In linear regression and path analysis models, wPTH was positively associated with WAZ. Vitamin D suppressed PTH, while FGF23 was positively associated with PTH. In path analysis models, higher magnesium was negatively associated with LAZ; FGF23 was positively associated and protein intake was negatively associated with LAZ, WAZ, and HCAZ. Higher maternal PTH in late pregnancy is unlikely to contribute to IUGR. Future studies should investigate maternal FGF23, magnesium and protein intake as regulators of fetal growth, particularly in settings where food insecurity and IUGR are public health problems.Intrauterine growth restriction (IUGR) reflects inadequate growth in-utero and is prevalent in low resource settings. This study aimed to assess the association of maternal delivery parathyroid hormone (PTH) – a regulator of bone turnover and calcium homeostasis – with newborn anthropometry, to identify regulators of PTH, and to delineate pathways by which maternal PTH regulates birth size using path analysis. This was a cross-sectional analysis of data from participants ( Length and head circumference at birth are important indicators of fetal skeletal growth and are correlated with indicators of IUGR (Intrauterine growth restriction (IUGR), or inadequate fetal growth, is associated with short- and long-term adverse health outcomes , 3, 4, 5 of IUGR , 7; for  of IUGR . In low- of IUGR , reducti of IUGR , 11.in vivo and clinical studies suggests that parathyroid hormone does not cross the placenta (Parathyroid hormone (PTH) is a peptide hormone that primarily regulates calcium homeostasis by binding to the PTH 1 Receptor (PTH1R) , 13, andplacenta , 15. As et al. reported that PTH was negatively associated with birth length and head circumference  pathways by which maternal PTH and its regulators may influence fetal growth. We hypothesized that PTH would be negatively associated with birth size due to a higher prevalence of calcium metabolic stress in this population. We also hypothesized that PTH would function as a mediator of the association of upstream regulators of PTH and birth size.This was a cross-sectional analysis of data from a subset of participants enrolled in the Maternal Vitamin D for Infant Growth (MDIG) Trial in Dhaka, Bangladesh . The MDIG trial was a double-blind, randomized placebo-controlled trial designed to estimate the dose-ranging effects of prenatal vitamin D supplementation  and postpartum supplementation , vs placebo on infant length at 1 year of age. Participants enrolled in the MDIG trial were co-supplemented with daily calcium (500 mg) and iron and folic acid . Detailed descriptions of the methods and results of the trial are described elsewhere , 35. AppHealthy pregnant women attending antenatal visits at the Maternal and Child Health Training Institute (MCHTI) at least 18 years of age and at 17–24 completed weeks of gestation at the time of the visit  were invited to participate in the MDIG trial. Detailed inclusion and exclusion criteria are described elsewhere , 35.n = 490). To increase the sample size to describe changes in PTH concentrations from mid-gestation to delivery in the absence of vitamin D supplementation, an additional 47 participants from the placebo group were also included in this study .A total of 537 mother–infant pairs were selected for this study  was administered at baseline to estimate habitual maternal calcium and protein intake (Supplementary Method 1). Calcium intake was expressed in milligrams per day (mg/day) and protein intake was expressed in grams of protein per kilogram body weight per day (g/kg/day).Crown-to-heel length, rump-to-knee length (RKL), weight, and head circumference were measured independently by two study personnel within 48 h of birth, based on a predefined protocol (Supplementary Method 2). Length was initially measured using a length board with a counter display and ball bearing mounted sliding footboard ; however due to frequent decalibration, it was changed to a wooden length board . A total of 128 infants (24%) were measured using the Harpenden length board and 402 infants (76%) were measured using the Shorrboard.Intergrowth-21st growth standards  were useMaternal specimens were collected and stored using a standard protocol (Supplementary Method 3). Assay information and performance indicators for all lab analyses are recorded in Supplementary Table 1.Maternal baseline and delivery plasma PTH concentrations were quantified using intact PTH (iPTH) and whole PTH (wPTH) sandwich ELISA kits . The iPTH assay measures concentrations of the whole 84 amino acid PTH peptide and long fragments that are missing the first few amino acids from the n-terminus because the epitope for the detection antibody is located in the middle of the peptide. The wPTH assay uses a detection antibody targeting the first four amino acids of the PTH protein, and therefore measures only the whole (bioactive) PTH peptide without any inactive fragments. Although wPTH may provide a more physiologically relevant measure of the active PTH peptide, we also present analyses using iPTH to compare to prior studies of the association of maternal PTH and birth size, all of which used iPTH assays , 22, 37.Maternal serum 25-hydroxyvitamin D (25(OH)D) concentrations were measured using high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) following methodology previously described . MaternaIf any biomarker analyses yielded unquantifiable values due to concentrations being below the standard curve detection limit, half the lowest standard of the assay was imputed for analysis (Supplementary Table 1). Values above the upper limit of detection were imputed as the highest standard curve concentration. For CRP, values that were above the upper limit of detection were imputed extrapolating from the standard curve (Supplementary Table 1).s.d., median , or frequencies and percentages. Maternal PTH, FGF23, CRP, and 25(OH)D were log-transformed due to right-skewing of the data. Participant characteristics were compared between women with baseline iPTH concentrations (17–24 weeks’ gestation) that were above or below the 80th percentile of the iPTH distribution (5.81 pmol/L). Similar to Hemmingway et al.  with birth LAZ, WAZ, and HCAZ, we used unadjusted and multivariable-adjusted linear regression models. A modified Poisson regression with robust error variance  was usedus items ), gravidus items , vitaminus items . Sensitin =142).To identify regulators of PTH, delivery iPTH and wPTH concentrations were each regressed on vitamin D treatment group, magnesium, FGF23, CRP, protein intake, and calcium intake in separate linear regression models. Multivariable models included all proposed regulators of PTH, maternal age, maternal education, asset index and gravidity. In sensitivity analyses, vitamin D treatment group was substituted with 25(OH)D concentrations in multivariable models, and analyses were limited to women randomized to receive placebo . From the path analysis model, we present direct, indirect (mediated) and total effects, which represented both associations and causal effects (when vitamin D supplementation was the predictor). Maternal calcium intake and delivery CRP concentrations were not included in the final path model as they did not explain a meaningful level of variance in delivery PTH and birth size, and did not improve model fit.P-values. We considered P-values less than 0.05 as statistically significant. Data were analyzed with Stata version 15.1 (StataCorp 2017).All results were presented as point estimates of the effect size, with 95% CIs and Participant characteristic and biomarker data, stratified by baseline iPTH concentration (measured at 17–24 weeks of gestation), are summarized in iPTH at delivery was significantly positively associated with LAZ, WAZ, and HCAZ in unadjusted linear regression models, but all estimates were attenuated and non-significant in multivariable linear regression models .Table 2There was no significant association between iPTH and birth size in any sensitivity or subgroup analyses (data not shown). Excluding infants who were measured using the Harpenden length board where LAZ was the outcome did not change inferences.wPTH was not associated with LAZ, WAZ and HCAZ in sensitivity and subgroup analyses, although effect estimates were all positive. Similarly, there were no associations between wPTH and SGA in multivariable subgroup analyses restricted to women randomized to the placebo group, mother-infant pairs with detectable wPTH, boys, and girls. There was, however, a positive association between wPTH and SGA in models adjusting for 25(OH)D in place of vitamin D treatment group; in models restricted to term born infants only; and in models restricted to infants with anthropometry collected within 24 h of birth (data not shown).Among covariates included in multivariable models, maternal protein intake was negatively associated with birth LAZ, WAZ, and HCAZ, whereas FGF23 concentrations showed positive associations with LAZ, WAZ, HCAZ, and RKL . Among mother-infant pairs randomized to the placebo group, maternal baseline PTH was not associated with newborn size (Supplementary Table 9).We used linear regression analyses to assess the association between hypothesized nutritional and endocrine factors and maternal PTH concentrations at delivery. Vitamin D supplementation suppressed iPTH and wPTH concentrations at delivery in a dose-dependent manner . Similar to linear regression models, vitamin D supplementation suppressed PTH at delivery in a dose-dependent manner; the lowest dose at which maximal suppression was achieved was the 16,800 IU/week group, with no additional suppression of PTH in the 28,000 IU/week group (Supplementary Tables 12 and 13). There was a significant negative direct and total effect of delivery 25(OH)D on PTH concentrations. The direct effect of vitamin D supplementation was not significant; however, the indirect effect of vitamin D supplementation was statistically significant, indicating the effect of prenatal vitamin D supplementation on delivery PTH was substantially mediated by delivery 25(OH)D  . Similarly, there was no vitamin D-wPTH or calcium-wPTH interactions relevant to the association of wPTH and infant weight .In a Bangladeshi cohort with a high prevalence of SGA, low dietary calcium intake, and high prevalence of vitamin D deficiency, we did not find strong evidence to support an important role for PTH in the regulation of fetal growth. Although there was a positive association between maternal delivery iPTH concentrations and birth length in a path analysis model, the effect sizes were small, and inferences were not supported by models adjusted for confounders. Similarly, while wPTH was positively associated with birthweight in path analysis and multivariable linear regression models, overall effect sizes were small. Effect estimates across all models assessing the association of iPTH and wPTH with birth anthropometry were positive, which was contrary to our hypothesized negative effect of maternal PTH on fetal growth. These results are generally consistent with the previously reported null effect of vitamin D supplementation on birth size in the main trial report .Morley and colleagues previously reported a positive association between late-pregnancy iPTH and birthweight in an Australian cohort . Althoug et al. D. If the observed positive association between iPTH and infant length, and between wPTH and infant weight in our path analysis models are true effects, then we would expect a negative effect of vitamin D supplementation on birth size. This is because the PTH-mediated effect of vitamin D supplementation on birth size is by definition the mathematical product of the direct effects of vitamin D on PTH and of PTH on birth size. Consistent with this notion, the observed indirect effect of vitamin D on birth size was negative, although effect estimates were small and not significant. In the MDIG trial, prenatal vitamin D supplementation indicated very small non-significant total negative effects on birth LAZ, WAZ, and HCAZ, compared to placebo . This maVitamin D also suppressed magnesium concentrations at the highest dose, with an apparent dose-dependent effect. Few studies have reported on the causal effect of vitamin D supplementation on magnesium concentrations. One study conducted in Iran found no effect of vitamin D supplementation  vs placebo on magnesium concentrations among hypertensive patients with vitamin D deficiency . Similarin vivo and clinical studies of patients with renal insufficiency . We were also unable to assess associations of venous cord PTH in this study, owing to large proportions of undetectable concentrations (>90%), which would have allowed us to measure the direct association of PTH in the fetal circulation with fetal growth. Lastly, we recognize the potential for selection bias in our analysis, since this study sample was chosen from an already selected group of participants in a randomized controlled trial.Our study had limitations that are important to acknowledge. The FFQ utilized in this study was non-quantitative and not previously validated, which may have reduced the accuracy of estimated total dietary calcium and protein intake. Women in the MDIG trial were co-supplemented with calcium which may have mitigated any association of calcium intake with PTH concentrations. Although many of the analyses were based on a cross-sectional observational design (e.g. variables simultaneously measured at birth), we leveraged the randomized placebo-controlled trial design of the MDIG trial to estimate causal effects of vitamin D supplementation on PTH, magnesium, and FGF23. The mediation analyses were grounded in the literature and specific In conclusion, maternal delivery PTH is not a biomarker of IUGR, and elevated maternal PTH at delivery does not appear to impair fetal skeletal growth in a population with a high prevalence of maternal undernutrition and IUGR. Future studies should aim to further examine the potential role of maternal FGF23, magnesium and protein intake in pregnancy on fetal growth.The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.The MDIG trial was funded by the Bill and Melinda Gates Foundation (OPP1066764).H Q, D E R, A D G, and N P designed research; H Q, D E R, E P, and A A M conducted research; H Q analyzed data; and H Q, and D E R wrote the paper. H Q and D E R had primary responsibility for final content. All authors read and approved the final manuscript.The authors wish to thank all MDIG trial participants, personnel and co-investigators; Dr Robert Bandsma at the Centre for Global Child Health (CGCH), The Hospital for Sick Children  for sharing laboratory resources for this project; Akpevwe Onoyovwi at the CGCH, The Hospital for Sick Children  for assistance with magnesium measurements; and Hayley Craig-Barnes and Ashley St. Pierre of the Analytical Facility for Bioactive Molecules (AFBM), The Hospital for Sick Children  for assistance with 25-hydroxyvitamin D, CRP, and FGF23 measurements. The MDIG trial was funded by the Bill and Melinda Gates foundation.


Bisphenols are endocrine disruptors that may be associated with altered fetal growth in humans, and they have similar biological functions to mimic hormones. In addition, aggregated chemicals showed an adverse effect although individual concentration was at a low level. However, most studies between bisphenols and birth outcomes have focused on the effect of individual bisphenol. Thus, we explored the associations of urinary bisphenol mixtures with birth outcomes. We conducted a prospective birth cohort study in South Korea. One hundred eighty mother-infant pairs were recruited from 2017 to 2019. Bisphenol A (BPA), bisphenol F (BPF), and bisphenol S (BPS) in one spot urine were analyzed using ultra-performance liquid chromatography–tandem mass spectrometry. We used two statistical approaches to examine potential associations of BPA, BPF, and BPS with birth weight and gestational age: (1) multivariable linear regression; (2) Bayesian kernel machine regression (BKMR). The geometric means of BPA, BPF, and BPS were 2.1, 0.2, and 0.1 μg/L, respectively. In stratified linear analyses by each median value, a higher BPF was positively associated with birth weight (g) . Mixture analyses using BKMR suggested an inverse association between bisphenol mixtures and birth weight. Our findings suggest that in utero bisphenol exposure may influence birth weight and that such relationships may differ considering non-linearity and the combined effect. Bisphenols are a class of endocrine-disrupting chemicals (EDCs) frequently used in manufacturing polycarbonate plastics and epoxy resins, which are found in various consumer products, such as plastic baby bottles, toys, and epoxy food-can linings ,2. DespiBisphenols influence on physiological receptors in different pathways . BPA canConsidering the toxicity of BPA and consumer concerns, manufacturers have been banned from using BPA in their products, with gradual transitions to using bisphenol analogs, such as BPF and BPS. Thus, BPF and BPS have been widely used in manufacturing BPA-free products ,15. SomeAlthough these previous studies found that exposure to environmental chemicals during pregnancy may be associated with adverse fetal growth, most did not consider the aggregate effect of environmental chemical exposure on infant health . Among tn = 8) and no available urinary bisphenol concentration data (n = 56). Therefore, 180 pregnant women were included in the final analysis. This study was approved by the Institutional Review Boards of National Cancer Center, Korea.The MAKE study was a community-based prospective birth cohort study in South Korea to examine the effects of maternal chemical exposure during pregnancy on fetal growth. Pregnant Korean women aged at least 18 years were eligible to enroll. The details of the MAKE study have been described previously . BrieflyEscherichia coli K12; Roche Biomedical, Mannheim, Germany) were added. The samples were enzymatically hydrolyzed for 16 h in a constant temperature bath at 37 °C and then cooled down by adding 100 μg/L of 2 N HCl. After solid phase extraction to remove impurities, the samples were eluted with methanol and then analyzed using ultra-performance liquid chromatography–tandem mass spectrometry .Spot urine samples were collected from each participant while visiting the center and then were frozen at −70 °C. To measure the urinary bisphenol concentrations, a 1-mL sample was transferred to a glass test tube, and then internal standards of 50 μg/L, 1 mL of 2 M sodium acetate, and 50 μg/L of β-glucuronidase  were performed such as linearity, accuracy, precision, and method detection limits. For quality control, seven samples with a concentrated standard 3 to 10 times the detection limit were measured with the same procedures mentioned above. The limit of detection (LOD) was calculated by multiplying the standard deviation of the seven replicates by 3.14 . The precision and accuracy measurements were calculated by multiplying by the relative standard deviation of more than five replicated measurements. The acceptable range of precision and accuracy was 85–115%. The correlation coefficient of the calibration curve was more than 0.999. The LOD for BPA, BPF, and BPS were 0.071, 0.083, and 0.020 μg/L, respectively.For external QC, each analytical laboratory regularly participated in international and national quality control programs. Internationally, all the laboratories participated in the 61st to 63rd programs of the German External Quality Assessment Scheme (G-EQUAS) and also participated in the domestic quality assurance program by the National Institute of Environmental Research (NIER) in South Korea. All the analytical results of the laboratories were qualified within the tolerance ranges by the managers of G-EQUAS and NIER.After delivery, we obtained birth information, including the birth weight (g) and gestational age (week) from medical record. Gestational age at delivery was estimated from the first date of the last menstrual cycle or the first date of ultrasonographic estimation if the date of the last menstrual period was unreliable or if a significant difference occurred between the last menstrual cycle date and ultrasonographic estimation date (>10 days).10-transformed for normality assumption. The urinary bisphenols were corrected for specific gravity (SG) and measured using a urine analyzer  to adjust the urinary dilution [Urinary bisphenol concentrations below the LOD were assigned to LOD/√2 , and alldilution . The SG-t-test to assess the differences in the birth weight and gestational age according to the maternal and infant characteristics. We selected potential confounders, known as influential factors, for bisphenol exposure and birth outcomes from previous studies with a directed acyclic graph (2) [We used Student’s ic graph . All theraph (2)  before pTo estimate the linear associations between each urinary bisphenol and birth outcomes, we used multivariable linear regression models using the SAS 9.4 software . We used three models: unadjusted model, multivariable-adjusted model, and mutually adjusted model.We conducted further analyses using Bayesian kernel machine regression (BKMR) , with thi , C is the concentrations of bisphenols, h denotes the unknown exposure-response function to be estimated, BKMR with a gaussian kernel function is used to estimate the individual and overall joint association of bisphenols with birth outcomes, and the formula is given by:outcomes .As BKMR calculates the high-dimensional estimation of the exposure-response surface, it can visualize these associations by defining the cross-sectional surface. Thus, we present the following in this study: (1) the univariate exposure–response relationship of one bisphenol with birth outcomes, considering that others are fixed at their median value and all the covariates have a constant value; (2) the association of one bisphenol increases by a certain percentile  with birth outcomes at various quantile values of others, considering that all the covariates have a constant value; (3) the bivariate exposure–response relationship of one bisphenol with birth outcomes at various quantile values of another bisphenol, considering that the other bisphenol is fixed at its median value and all the covariates have a constant value; (4) the overall joint association of all bisphenols increase by five percentiles with birth outcomes as referenced to their 50th percentile, considering that all the covariates have a constant value.10-transformed values and centered to handle skewed data, and all the BKMR models were adjusted for potential confounders. BKMR was implemented with the R package bkmr using R software .The BPA, BPF, and BPS concentrations were scaled to logThe detection rates of bisphenols above the LOD in urine samples followed the order of BPA (96.2%), BPF (84.4%), and BPS (66.1%). The SG-corrected geometric means (GM) of the BPA, BPF, and BPS concentrations were 2.1, 0.2, and 0.1 μg/L, respectively . The matp-value = 0.82; BPF: β = 38.5, 95% CI: −18.1 to 95.1, p-value = 0.18) and gestational age . However, BPS was negatively associated with the birth weight  and gestational age ; additionally, all the linear associations were not statistically significant. However, after stratified analyses by the median concentration of each bisphenol, a higher BPF level was significantly associated with increased birth weight   .We conducted BKMR using component-wise variable selection to examine the potential nonlinear and interactive effects and overall effect of bisphenols on the birth outcomes, adjusting for potential confounders. The estimated PIPs on the birth weight for BPA, BPF, and BPS were 0.11, 0.78, and 0.48, respectively, and the PIPs of the gestational age for BPA, BPF, and BPS were 0.21, 0.31, 0.25, respectively. In this study, we found nonlinear associations of BPF and BPS on birth weight. For BPF, an increase in BPF from the 10th to 50th percentile (0.1 to 0.2 μg/L; To examine potential pairwise interactions among the bisphenols, particularly due to the nonlinearity for BPF and BPS, we estimated the predicted change in birth weight and gestational age, considering the other bisphenol patterns at 25th, 50th, or 75th percentiles. Finally, we also examined the overall effect of bisphenol mixtures on birth outcomes. In this prospective birth cohort study, we examined the associations of the gestational concentrations of bisphenols with birth weight and gestational age. We found that higher BPF levels were significantly associated with increased birth weight. We observed a non-linear association of BPF and BPS on birth weight and increasing levels of the bisphenol mixture were associated with decreased birth weight. However, we found no changes in gestational age.In the current study, urinary BPA levels were much higher than those of its analogs. The results of our individual bisphenol analyses were similar to those previously reported in investigations using the MAKE study . ComparePrevious studies have found that maternal bisphenol exposure is associated with birth weight. However, the impact of prenatal exposure to BPA on size at birth is unclear because of the inconsistent findings from current epidemiological studies . Our resSimilar to BPA, two birth cohort studies reported that maternal exposure to BPS and BPF was inversely associated with size at birth ,17, whilPrevious studies have assessed the association between individual chemical biomarkers and birth outcomes. Few have examined the effect of aggregate environmental exposures on birth outcomes ,40,41,42The metabolism of BPS and BPF have not been well studied. However, several experiments have showed that BPF metabolism and distribution are similar to those of BPA . BPA expOur study has several limitations. First, the specificity of the bisphenol mixture exposure assessment has not been evaluated in other studies. Second, our study sample size was small, which may reduce the statistical power to obtain the sufficient precision of our estimates . FinallyHigher exposure to BPF is associated with increased birth weight. However, the overall joint association of bisphenol mixture exposure with birth weight suggests an inverse association with birth weight. Thus, individual chemical exposure and mixture exposure may have different effects on the same health outcome. Further studies are required to substantiate these findings considering non-linearity and the combined effect.


Gestational age at birth is a critical factor for perinatal and adulthood outcomes, and even for transgenerational conditions’ effects. Preterm birth (PTB) (prematurity) is still the main determinant for infant mortality and morbidity leading cause of infant morbidity and mortality. Unfortunately, preterm birth (PTB) is a relevant public health issue worldwide and the global PTB rate is around 11%. The premature activation of labor is underlined by complex mechanisms, with a multifactorial origin influenced by numerous known and probably unknown triggers. The possible mechanisms involved in a too early labor activation have been partially explained, and involve chemokines, receptors, and imbalanced inflammatory paths. Strategies for the early detection and prevention of this obstetric condition were proposed in clinical settings with interesting results. Progesterone has been demonstrated to have a key role in PTB prevention, showing several positive effects, such as lower prostaglandin synthesis, the inhibition of cervical stromal degradation, modulating the inflammatory response, reducing gap junction formation, and decreasing myometrial activation. The available scientific knowledge, data and recommendations address multiple current areas of debate regarding the use of progesterone in multifetal gestation, including different formulations, doses and routes of administration and its safety profile in pregnancy. Preterm birth is defined by the World Health Organization (WHO) as delivery before 37 completed weeks of gestation. About 85% of these premature births occur at 32 to 36 weeks, 10% are born at 28–31 weeks, and 5% at <28 weeks of gestation (extremely preterm babies).Being born too soon is an important cause of infant deaths from prematurity every year, and many preterm newborns have long term disabilities. About 15 million babies are born preterm annually, with an increasing trend in cases rates worldwide, putting the global PTB rate at 11% ,3.There is growing evidence that the progesterone can be useful in high risk pregnancies for preterm birth. The use of progestogens has been extensively studied over the years and it is still a topic of interest in current research ,11,12,13The complex pathogenesis of preterm labor activation makes reliable prediction difficult . An obstExtensive data reported that the ultrasound measurement of CL at mid-gestation may be a useful strategy for predicting the risk of pretem birth delivery for both singleton and twin pregnancies ,20,21,22The history of progesterone (PG) is long and characterized by numerous and fascinating chronological steps, and it is probably destinated to have a “never-ending history”, as discussed in a recent paper ,27. ProgNowadays, the pharmacokinetic and pharmacodynamic features of progesterone are well-known.The understanding of the pharmacodynamics of progesterone in preterm labor prevention is based on the evidence that it relaxes the uterus throughout pregnancy by inhibiting the expression of estrogen receptor alpha (ER-a) and reducing sensitivity to estrogen . OverallThe route of administration seems crucial in determining the optimal pharmacodynamic profile of P4 and in obtaining the desired clinical effects. Most of the body of scientific evidence regards the vaginal, intramuscular and oral routes, as discussed below. The most important revolution in theme of progesterone is the development of micronization process, which led to further optimization of clinical effects and objectives deriving from its use. The micronization of progesterone and its suspension in oil-filled capsules was first studied in the late 1970s; this allowed progesterone to be absorbed more efficiently by the traditional oral route .Nowadays, micronized progesterone products are largely preferred and used in obstetrics (and not only in this field) for many medical conditions, including threatened miscarriage, recurrent pregnancy loss and PTB prevention ,33,34. BThe current best approach to limit the preterm birth burden is based on early detection risk and prevention by multilevel and even combined strategies. In recent years, international and national societies have shown a great need to identify and manage women at risk of delivering prematurely, developing and sharing recommendations that are not absolute but which are, nevertheless, useful .The traditional method of antenatal screening is based on an accurate history based on factors such as maternal age, race, smoking status, and previous and current obstetric history. The available risk scoring systems, which attempt to define the pregnancy’s level of risk, have been shown to have a scarce detection rate and a high false-positive rate . An alteThus, measuring cervical length by TVU is a simple and effective test for the prevention of PTB, but routine CL screening is not clearly recommended by some international societies ,39,40,41The FIGO Working Group on Best Practice in maternal-fetal medicine was clear in its statement in favor of the universal screening of pregnant women by mid-trimester TVU evaluation of the cervical length as a useful intervention to decrease preterm births in pregnant women with a short cervix ,42. SimiOnce risk assessment is established, the choice on how to manage risk may involve one or a combination of several preventive strategies. Regarding progesterone use, differences exist worldwide.Given the association of cervical shortening with preterm birth, several interventions aimed at decreasing the PTB rate have been investigated, including intramuscular 17-hydroxyprogesterone caproate (17-OHPC), cerclage, cervical pessary, and vaginal progesterone ,45,46,47The National Institute of Child Health and Human Development (NICHD) Maternal–Fetal Medicine Units Network conducted a multicenter double-blind randomized controlled trial of 463 women with a singleton pregnancy and prior spontaneous preterm birth between 16 and 36 weeks who received 17-OHPC or placebo. Treatment with 17-OHPC was associated with a 34% reduction in recurrent preterm birth at <37 weeks of gestation (from 54.9 to 36.3%), as well as significant reductions at <32 and <35 weeks and decreased infant complications, such as intraventricular hemorrhage, necrotizing enterocolitis, and need for supplemental oxygen . In 2011A 2020 statement from SMFM concludes that providers can reasonably continue to use 17-OHPC in women with a risk profile similar to that of the enrollees in the NICHD study . Given tThe clinical advantage of vaginal progesterone has been largely investigated and supported in women with prior spontaneous preterm delivery. While subsequent studies have produced mixed results, a 2019 meta-analysis readdressed the question of the optimal intervention for women with a prior preterm birth and confirmed that vaginal progesterone treatment was associated with a reduction in recurrent preterm birth at <34 weeks  and <37 weeks  .At the present, the debate on intramuscular 17-OHPC, vaginal progesterone and which route and formulation is better is still open. The EPPPIC study group reported results of a meta-analysis, in which data from 31 trials were included. The authors considered trials of both singleton and multifetal pregnancies comparing vaginal, intramuscular and oral progesterone administration with control, or with each other. Compared with controls, both the vaginal route and the intramuscular 17-OHPC reduced the risk of PTB before 34 weeks for singleton pregnancies in high risk women, with a 22% reduction in the relative risk (RR) for participants who received vaginal progesterone , and 17% reduction for those received 17-OHPC  . ImportaRegarding the utility of oral progesterone administration as preventive strategy in high risk patients, evidence to support its use in clinical routine practice is still inconsistent .A recent study reported that oral progesterone appears to be effective for the prevention of recurrent preterm delivery and reduction in perinatal morbidity and mortality in asymptomatic singleton pregnancies compared with placebo. More adverse effects with oral progesterone therapy compared with placebo were reported, although none were serious. Thus, future randomized studies comparing oral progesterone with other available therapies for the prevention of recurrent preterm birth are needed .+0 and 33+6 weeks’ gestation. Post hoc time-to-event analysis led to the suggestion that progesterone may reduce the risk of spontaneous birth before 32 weeks’ gestation in women with a cervical length of <30 mm, and it may increase the risk for those with a cervical length of ≥30 mm [Twin pregnancies are associated with a several-fold greater perinatal mortality than singleton pregnancies. PTB Prematurity is an important contributor, with about 50% of twin pregnancies delivering before 37 weeks and 10% delivering before 32 weeks . Trials f ≥30 mm . In concData regarding the efficacy of combining different approaches, such as intramuscular progesterone with or without vaginal progesterone and with or without cervical cerclage and Arabin pessary, are limited, not unanimous, but in evolution. The utility of combined treatment with history-based cerclage and intramuscular 17-OHPC is unclear, and small retrospective studies have reported mixed results ,65. The The safety profile of progesterone on newborn health is another topic of growing interest among experts. Many questions remain unexplained, particularly the long-term safety concerns and also whether the use of progestagens may or not improve neonatal and childhood outcomes.The results of a meta-analysis suggest that the administration of progestogen for preterm birth prevention does not appear to negatively affect neonatal mortality in single or multiple pregnancies regardless of the route of administration . MoreoveA recent systematic review examined the potential long-term effects of prenatal progesterone treatment on child development, behavior and health: the authors did not find evidence of benefit or harm in offspring prenatally exposed to progesterone treatment for PTB prevention . There iThe current scientific and clinical evidence suggest that cervical length screening and vaginal progesterone use, eventually combined with cervical cerclage or Arabin pessary, may help to contain or reduce the burden of preterm delivery birth, when used in the appropriate target populations of pregnant women. The current data and recommendations address multiple controversial topic areas regarding the role of progesterone for PTB prevention in multi-gestational pregnancies multifetal gestation, its different formulations, dosages, routes of administration and safety profile in pregnancy. Overall, a growing body of studies are in agreement in identifying progesterone, especially the vaginal formulation, as a keystone among the preventive PTB strategies in well-defined high-risk categories.


Exposure to bisphenols may affect fetal growth and development. The trimester-specific effects of bisphenols on repeated measures of fetal growth remain unknown. Our objective was to assess the associations of maternal bisphenol urine concentrations with fetal growth measures and birth outcomes and identify potential critical exposure periods.In a population-based prospective cohort study among 1379 pregnant women, we measured maternal bisphenol A, S and F urine concentrations in the first, second and third trimester. Fetal head circumference, length and weight were measured in the second and third trimester by ultrasound and at birth.p-value< 0.05) across pregnancy. When focusing on specific critical exposure periods, any detection of first trimester bisphenol S was associated with larger second and third trimester fetal head circumference (difference 0.15 (95% CI 0.05 to 0.26) and 0.12 (95% CI 0.02 to 0.23) SDS, respectively) and fetal weight (difference 0.12 (95% CI 0.02 to 0.22) and 0.16 (95% CI 0.06 to 0.26) SDS, respectively). The other bisphenols were not consistently associated with fetal growth outcomes. Any detection of bisphenol S and bisphenol F in first trimester was also associated with a lower risk of being born small size for gestational age (Odds Ratio 0.56 (95% CI 0.38 to 0.74) and 0.55 (95% CI 0.36 to 0.85), respectively). Bisphenols were not associated with risk of preterm birth.An interquartile range increase in maternal pregnancy-averaged bisphenol S concentrations was associated with larger fetal head circumference  0.01 to 0.34) standard deviation scores (SDS), Higher maternal bisphenol S urine concentrations, especially in the first trimester, seem to be related with larger fetal head circumference, higher weight and a lower risk of being small size for gestational age at birth.The online version contains supplementary material available at 10.1186/s12940-021-00747-6. Bisphenols are endocrine disrupting chemicals and are widespread in food packaging, thermal paper receipts and personal care products –3. It haWe examined, among 1379 women participating in a population-based cohort study, the associations of bisphenol urine concentrations at three time points in pregnancy, with fetal head circumference, length and weight measured at two time points during pregnancy and at birth and with the risks of preterm birth and being born small size for gestational age.This study was embedded in the Generation R Study, a population-based prospective cohort study from fetal life onwards in Rotterdam, the Netherlands . The stuBisphenol concentrations were measured in a spot urine sample obtained from each participant at early pregnancy , mid-pregnancy  and late pregnancy . These periods were considered first, second and third trimester. Urine samples were collected between February 2004 and July 2005. Details on collection, transportation, and analysis methodology have been described previously . BrieflyIn second and third trimester, we measured fetal head circumference and femur length to the nearest millimeter using standardized ultrasound procedures . Estimat2) was calculated. Maternal daily caloric intake was estimated from a validated food frequency questionnaire filled in at enrollment, covering average intake in first trimester [We obtained information on maternal age, parity, educational level, ethnicity, pre-pregnancy weight, folic acid supplement use, smoking habits and alcohol consumption from questionnaires during pregnancy. At enrollment, maternal height was measured and pre-pregnancy body mass index  and no further stratified analyses were performed. To maintain statistical power and reduce bias related to missing data on covariates, we performed multiple imputation according to the Markov Chain Monte Carlo method. The percentage of missing values for covariates ranged from 0 to 25%. Ten imputed datasets were created and no substantial differences were found between original and imputed datasets. To correct for multiple hypothesis testing, each p-value was compared with a threshold defined as 0.05 divided by the effective number of independent tests estimated based on the correlation between the exposures  [nlme for the linear mixed effects models.After substitution of concentrations below the LOD with LOD/√2, we natural log-transformed the creatinine-adjusted bisphenol urine concentrations to reduce variability and account for right skewedness of the distribution and standardized by the interquartile range to ease interpretation of effect sizes. We assessed Pearson correlations between all bisphenols. We performed linear mixed effects models to assess associations of the average bisphenol urine concentrations over pregnancy with head circumference, length or weight SDS repeatedly measured in second and third trimester and at birth. We inspected the pattern of associations using generalized additive models, and no clear non-linearity was observed. All models included a random intercept and slope. We additionally included an interaction term between pregnancy-averaged bisphenol urine concentrations and gestational age to allow the exposure-outcome association to change across pregnancy. To identify potential critical exposure periods, we assessed associations of bisphenol concentrations in first, second and third trimester with outcome measurements in second and third trimester and at birth using linear regression models. For these analyses, we examined only outcomes at the same or subsequent time points as the exposure. Due to the high percentage of concentrations the below LOD for BPS and BPF, we first performed these models using the bisphenols categorized as detected (above the LOD) and undetected (below the LOD) and then repeated these models using continuous bisphenol concentrations as a sensitivity analysis. We performed binary logistic regression models to assess the associations of detection of bisphenols in first, second and third trimester with risks of preterm birth and small size for gestational age at birth. Then, we repeated these models using continuous levels of bisphenols during first, second and third trimester and pregnancy-averaged bisphenol urine concentrations. Due to the low number of preterm births and potential lack of power, as a sensitivity analysis, we performed linear regression models to assess the associations of bisphenol urine concentrations, categorized as detected and undetected and continuously, with gestational age at birth. To examine the independent associations of maternal first, second and third trimester bisphenol concentrations, we simultaneously included in one model the exposures during all three trimesters, creating a mutually adjusted model. Potential confounders were identified based on graphical criteria for confounding by visualizing a directed acyclic graph  . We pres2. In total, 2.5% of all women had a preterm delivery. We observed low correlations between bisphenol urine concentrations across pregnancy and between individual bisphenols within the same trimester . No associations were observed for maternal pregnancy-averaged bisphenol concentrations with fetal length and weight. Basic models are shown in Supplemental Table Table Trimester-specific and pregnancy-averaged total bisphenols and BPA, BPS and BPF, either categorized as detected and undetected or continuously, were not associated with risk of preterm birth Table . Any detWe observed, in a population-based prospective cohort study, that higher maternal BPS urine concentrations, especially in first trimester, were associated with larger fetal head circumference and higher weight and lower risk of small size for gestational age at birth. No consistent associations were observed for the other bisphenols. Bisphenols are used in many consumer products –3. FetalOf the three meta-analyses concerning BPA and birth outcomes, two reported no consistent associations of fetal exposure to BPA with weight, length or head circumference at birth, while one reported positive associations with birth weight –8. Two sPrevious studies assessing the associations of maternal BPS urine concentrations with fetal growth measures during pregnancy and at birth showed inconsistent results , 29–31. Two studies investigating maternal BPF urine concentrations during pregnancy showed an inverse relationship with birth weight , 30. ThrThe availability of repeatedly assessed maternal bisphenol urine concentrations during pregnancy enabled us to investigate windows of vulnerability to exposure. We observed differences in associations according to trimester of exposure, suggesting that first trimester might be a particularly sensitive window to exposure. The observed associations might be mediated by the rapid placental development that occurs during early to mid-pregnancy. BPA inhibits proliferation and invasion of human trophoblast cells –37, and The major strengths of this study were the large sample size, the population-based cohort design from early life onwards, the availability of three urine measurements of bisphenol concentrations, and the use of repeated fetal growth measures during pregnancy and at birth. No substantial differences were observed between women in this subgroup and in the broader cohort and thus, although it cannot be excluded, selection bias seems unlikely . In thisFetal exposure to BPS, especially in the first trimester, seems to be related with larger fetal head circumference and higher weight and a lower risk of small size for gestational age at birth. BPA, BPS and BPF were not associated with the risk of preterm birth. Future studies in contemporary cohorts with possibly higher exposure levels are needed to further investigate the associations of newer bisphenols with fetal growth and adverse birth outcomes and to clarify the importance of the first trimester as a particularly sensitive window to exposure.Additional file 1: Supplemental Material Bisphenols. Tables containing additional subscriptive data and results of sensitivity analysis.


The neurophysiological mechanisms underlying executive function deficits in very preterm born children still remain unclear. Moreover, evidence on factors that can be modified by behavior and exert an influence on these deficits is lacking. The present case-control study examined the association between very preterm birth and neurophysiological indices of response inhibition (i.e. the N200-P300 complex) as well as the potential mediation of this association by aspects of physical fitness. 54 children born very preterm completed a submaximal cycling ergometer test and a motor skill test battery. Event-related potentials elicited by a Go/NoGo task were recorded using electroencephalography. Cases were then matched to full-term children (age: 11 ± 0.7 y). A higher error rate on NoGo trials was found in children born very preterm compared to those born full-term. Path-analyses further revealed that very preterm birth was associated with decreased NoGo P300 amplitude. Motor skills, but not aerobic fitness, fully mediated this association. In early adolescence, very preterm birth is associated with less effective recruitment of attentional resources for stimulus evaluation processes. The improvement of motor skills rather than cardiorespiratory fitness appears promising for reducing this specific impairment in cognitive control. WhereasAmong different neuroimaging methods, event-related potentials (ERPs) recorded via electroencephalography provide an opportunity to study neurocognitive processes. In this respect, a review on auditory ERPs in infants has primarily linked cognitive impairments with late components and mismatch negativity in particular . While tAmong a variety of factors, aspects of physical fitness need to be considered as potential mediators. Preterm birth is related to persistent deficits in cardiorespiratory fitness (CRF)  and motoThe present case-control study aimed to investigate the association between very preterm birth and behavioral as well as neurophysiological indices of response inhibition  during the transition from childhood to adolescence as well as their mediation by aspects of physical fitness. By accounting for interrelations between motor skills and CRF, their individual contributions to very preterm birth-related response inhibition deficits are examined. Based on the available evidence, we expected an association of very preterm birth with higher error rates and lower P300 and N200 amplitudes , 2019. M22.1Very preterm children (VPC) were recruited from the University Childrens’ Hospital Basel and the Kantonsspital Aarau and matched with full-term peers. Data for full-term control (FTC) cases were collected in a parallel study in the same region, which used identical assessments. Inclusion criteria were 9–13 years of age, right-hand dominance, corrected-to or normal vision as well as very preterm birth for cases (≤32 weeks of gestation) and full-term birth for controls (≥37 weeks of gestation). Common exclusion criteria were any acute or chronic diseases, which were classified as a contraindication for exercise and/ or which impaired the practicability of the scheduled exercise session . Additionally, full-term children with a mental disorder and preterm children with structural epilepsy and/or an intelligence quotient <85 were deemed ineligible. After receiving detailed information on study procedures, written informed consent was obtained from legal guardians of the participants. The study procedures followed the guidelines of the Declaration of Helsinki and were approved by the local ethics committee.2.2Participants completed a Go/NoGo task with simultaneous recording of ERPs elicited by the task. To assess socioeconomic status, psychopathology and moderate-to-vigorous physical activity (MVPA), they were asked to fill in the Family Affluence Scale (FAS), the Strengths and Difficulties Questionnaire (SDQ) and the 7-day physical activity recall protocol. Following the administration of the intelligence quotient screening items of the Intelligence and Development Scales-2 (IDS-2) and the collection of anthropometrics, participants’ motor skills and CRF were assessed using the Movement Assessment Battery for children-2 (MABC-2) and the physical work capacity test (PWC170). All measurements were performed during a single laboratory visit, with surrounding noise reduced to a minimum and at an environmental temperature of 21−22 °C.2.3The MABC-2 consists of age-appropriate fine and gross motor tasks that assess manual dexterity (three items), balance skills (three items) as well as aiming and catching (two items) . StandarPrior to the PWC170, participants received a heart rate monitor with a chest belt . The initial workload was based on the participants’ body weight  and increments depended on the heart rate within the last seconds of each 2-min stage . When th2.4The Go/NoGo task was administered with E-Prime 3.0  and included Go trials (30 %), more frequent Go trials (40 %) and NoGo trials (30 %). Participants were instructed to press a button on both Go trial types, but to suppress their motor response on NoGo trials. Speed and accuracy were equally emphasized. Visual stimuli were 10 different two-dimensional, grey geometric shapes  with contour lines drawn either in pink, yellow or blue color  arranged according to the 10:10 system (with AFz as ground). Scalp impedance was reduced to 10 KΩ or lower (≥90 % electrodes) by applying a highly conductive gel. Data was referenced to Cz, amplified and digitized at 500 hz . Offline processing of data was conducted with BESA Research 7.0 . Adaptive artefact correction was performed on blinks using spatial filtering based on artefact and brain activity topographies . In shor2.6t-Tests and rejected at p < 0.05. Model fit was tested for all models and considered good at RMSEA≤0.08 and χ2/df≤2 . The FUZZY plugin was employed for case-control matching based on sex and age. Following the verification of the Gaussian distribution of data with the Shapiro Wilk test, one-way ANOVAs were applied to compare participants’ characteristics  and physical fitness  between VPC and FTC. To guide the selection of potential confounders, zero-order correlations examined the relation between participants’ characteristics, physical fitness and behavioral as well as ERP outcomes. Participants’ characteristics showing a statistically significant and/or at least moderate correlation with one or more mediators and/or outcomes were controlled for in subsequent path-analyses. Using pre-specified models, the relations of very preterm birth  with behavioral performance (model 1a) and event-related potentials elicited from NoGo (model 2a) and Go trials (model 3a) were examined. In the next step, MABC-2 score and PWC170 were introduced to investigate whether these aspects of fitness mediated the relation of very preterm birth with behavioral performance (model 1b) and event-related potentials elicited from NoGo (model 2b) and Go trials (model 3b). Interrelations among mediators, behavioral and ERP outcomes were accounted for by estimating their covariances. Additionally, participants’ characteristics with a potential confounding effect (as identified in zero-order correlations) were also controlled by covariance estimation. Standardized regression coefficients were calculated to estimate the relative strengths of the examined associations. Furthermore, the hypothesis that coefficients in path-analyses equal zero was examined with  χ2/df≤2 .33.1F = 4.21, η² = 0.040, p = 0.040, and lower MABC-2 score than FTC, F = 4.21, η² = 0.040, p = 0.040 . Whereas no group differences were found for age, weight, body mass index, MVPA, PWC170, IDS-2 and FAS scores, VPC showed a higher SDQ score,  = 0.040 . With re = 0.040 . Behavio3.2p < 0.001, and omission error rates, β=0.21, p = 0.024. Following the inclusion of MABC-2 score and PWC170 (model 1b), there was a decrease of regression coefficients from moderate to small magnitude for commission error rate and small to negligible magnitude for omission error rate  showed that very preterm birth was associated with higher commission, β = 0.31, ror rate . This re3.3p = 0.014. When MABC-2 score and PWC170 were included to investigate mediating effects (model 2b), this association decreased and did no longer reach statistical significance . After including the mediators (model 3b), these associations remained unchanged . Pre-spe4The investigation of behavioral performance revealed that very preterm birth was associated with high commission and omission error rates, even when reaction time was accounted for. On a neurocognitive level, very preterm birth was further associated with a decreased P300 amplitude in the NoGo condition. When indirect effects via aspects of physical fitness were tested, motor skills mediated the relation of very preterm birth with both behavioral performance and the NoGo P300 amplitude.The present findings on the N200-P300 complex broaden the understanding of very preterm birth-related developmental abnormalities in response inhibition processes, which seem to persist at least into preadolescence. Whereas conflict monitoring indexed by the N200 amplitude was not associated with birth status, a lower P300 amplitude elicited from NoGo trials was found in VPC compared to FTC. This pattern of results is consistent with a previous study that examined ERPs elicited by a similar cognitive task . The NoGWith regard to physical fitness, VPC showed lower proficiency in motor skills and a tendency towards lower CRF than FTC. However, only motor skills mediated the association between very preterm birth, behavioral performance and the NoGo P300 amplitude. This is a first indication that the improvement of motor skills may benefit response inhibition by more effective recruitment of attentional resources for stimulus evaluation. In this respect, motor skills have previously been linked with the inhibitory aspect of executive function . The engk = 26) rather than response inhibition (k = 2). Thus, a moderation of the association between CRF and inhibitory control by its subtype cannot be ruled out. In the context of the present study, this implies that the promotion of motor skills rather than CRF has potential for counteracting the impaired cognitive control process indexed by reduced P300 amplitude in VPC.In contrast to motor skills, CRF did not mediate the association between very preterm birth and decreased NoGo P300 amplitude. Based on the inspection of regression paths, mainly the absence of a correlation between PWC170 and P300 amplitude accounted for this. It should be noted that this finding is in conflict with a previous review reporting strong evidence for a higher P300 amplitude in individuals with high CRF . HoweverAlthough the present findings provide first indications on the aspect of fitness that should be targeted to improve response inhibition, they should be interpreted with caution due to the cross-sectional design. Moreover, it remains unclear whether the mediating role of motor skills can be generalized to other components of executive function. Similarly, no conclusions can be drawn on the role of gestational age among preterm children, meaning that those born late preterm may lack a decreased NoGo P300 amplitude. The same applies to a potential influence of the age at assessment. Thus, the present findings provide no indication on whether the observed NoGo P300 abnormalities persist or are no longer detectable in later stages of life. With regard to the methodology, the current study was limited to the examination of the N200-P300 complex due to the chosen Go/NoGo paradigm, so that it remains unclear if VPC also show abnormalities in other processes related to response inhibition. Furthermore, despite the use of case-control matching and the consideration of many confounders, not all potential sources of variance in the mediators and outcomes could be accounted for . Additionally, only motor skills and CRF were assessed, which allows no conclusions on the role of other aspects of physical fitness for cognitive control processes in VPC.5In preadolescence, children born very preterm show impaired response inhibition in comparison to their full-term peers. On a neurocognitive level, this becomes evident by a reduced engagement of focal attention for evaluation processes that guide the subsequent selection of an appropriate motor response or its suppression. The associations of very preterm birth with both behavioral and neurocognitive impairments in cognitive control are mediated by motor skills. This provides a first indication that interventions should target such skills to reduce preterm birth-related deficits in response inhibition.Data will be made available on request to the corresponding author.Forschungsfonds of the University of Basel. The collection of data on full-term children was funded by the OPO Foundation and the Freiwillige Akademische Gesellschaft Basel.The collection of data on very preterm children was funded by the The authors report no declarations of interest.


The prevalence of preterm birth in Bangladesh is estimated to be 19.1%, the highest in the world. Although prenatal exposure to several metals has been linked with preterm birth, fewer prospective studies have investigated the socioeconomic factors that affect metal exposure, leading to preterm birth risk.We aim to identify novel metal biomarkers and their critical exposure windows, as well as the upstream socioeconomic risk factors for preterm birth in rural Bangladeshi, to shed light for future interventional strategies.This study included data from 780 mother–offspring pairs, who were recruited to participate in a prospective birth cohort in Bangladesh (2008–2011). Serum concentrations of 19 metals were measured in the first and second trimesters using inductively coupled plasma mass spectrometry. Mediation analysis was performed to explore the upstream socioeconomic factors that affect the risk of preterm birth mediated via metal exposure concentrations.Early pregnancy exposure to serum zinc, arsenic, and strontium and mid-pregnancy exposure to barium were significantly associated with risk of preterm birth. Furthermore, younger marriage age was associated with an exponential increase in the risk of preterm birth, and women who married after 18 years old had a considerably lower risk of preterm birth. Mediation analysis indicated that these four elements mediated 30.2% of the effect of marriage age on preterm birth.This study indicated that maternal serum metal exposure mediates the impact of child marriage on the increased risk of preterm birth via metal exposures. The findings shed light on the mechanisms underlying such association and provide insights into future interventional strategies. Preterm birth is associated with a high degree of immature organs. Infants born preterm (before 37 completed weeks of gestation ) are at Preterm birth results from the joint effects of various socioeconomic and demographic factors including, but not limited to, race, low socioeconomic status, multiple pregnancy, higher maternal age, history of abortion, pregnancy complications, and child marriage (marriage or union before the age of 18) . At a ceTherefore, taking advantage of the well-established birth cohort in rural Bangladesh, we measured the concentrations of 19 metals in maternal serum samples simultaneously in the first and second trimesters using inductively coupled plasma mass spectrometry (ICP-MS). We aimed to identify novel metal markers, critical exposure windows, and used mediation analysis to identify upstream socioeconomic effects factors that affect metal exposure levels, thus increasing the risk of preterm birth in rural Bangladesh which will provide insights into future interventional strategies.The Bangladesh birth cohort was established during 2008–2011, as previously described . The incg for 10 min to obtain blood serum. All containers used in the experiments were cleaned by soaking in 10% nitric acid (HNO3) for 24 h and rinsing several times with 18 Ω deionized water. Before analysis, 60 μL serum was diluted to 1.8 mL with 1% (v/v) HNO3, 0.1% (v/v) Triton X-100, and 10 μg/L internal standards.Peripheral venous blood specimens were collected in EDTA tubes after an overnight fast. Samples were stored at 4 °C, shipped to the Trace Metals Laboratory at the Harvard Chan School, and subsequently centrifuged at 1600 × 3 plus 10 μg/L internal standards including Sc, Y, In, Tb, and Bi; Appendix Table e transformed before statistical analysis. Serum levels of Mn, Cd, and U were less than the LOD in more than 50% of the testing samples: Mn , Cd , and U , which were additionally dichotomized to “detected” versus “non-detected” for subsequent analyses  at School of Public Health, Nanjing Medical University. The target metals included sodium (Na), magnesium (Mg), potassium (K), calcium (Ca), manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), arsenic (As), rubidium (Rb), strontium (Sr), molybdenum (Mo), cadmium (Cd), antimony (Sb), barium (Ba), mercury (Hg), thallium (TI), and uranium (U). The protocol for metal analysis was adapted from a previous report . The limPreterm birth is defined as a live birth before 37 completed weeks of gestation. Healthcare workers attended all births and collected detailed birth records. Gestational age was determined through ultrasonography by a licensed general practitioner using either the gestational sac mean diameter if the pregnancy was between 4 and 7 weeks, or the crown-rump length if the pregnancy was between 7 and 16 weeks . Other dt-test or Mann–Whitney U test for continuous variables depending on the data distribution , 95% confidence interval (CI), and P value for the risk of preterm birth. Sociodemographic factors, which were differentially distributed in the preterm birth and normal birth groups , and two-sided P < 0.05 was considered statistically significant unless stated otherwise.Notation Demographics of the 780 mothers are described in Table q value < 0.05) , As , and Sr  in the first trimester were significantly associated with preterm birth   were significantly associated with the risk of preterm birth (FDR-05) Fig. . We analβ = 0.01 , P = 3.9 × 10−03; As: β = −0.06, P = 1.4 × 10−04; Sr: β = 0.02 , P = 1.6 × 10−03 for the first trimester; Ba: β = −0.11 , P = 0.01 for the second trimester) , As , and Sr  during the first trimester  (Appendix Table Child marriage of girls (marriage age < 18 years old) is a risk factor for preterm birth . In thister Fig. . These tIn this study, dozens of maternal serum metals were repeatedly evaluated at two timepoints during pregnancy in a prospective birth cohort in Bangladesh. Serums Zn and Sr in the first trimester appeared to be protective against preterm birth, whereas serum As in the first trimester was positively associated with the increased risk of preterm birth. In addition, serum Ba in the second trimester was associated with the increased risk of preterm birth. Furthermore, marriage age was associated with an exponential increase in the risk of preterm birth, and women married after age 18 years old had a considerably lower risk of preterm birth. Mediation analysis indicated that these four elements together mediated nearly one-third (~30%) of the effect of marriage age on preterm birth.Not surprisingly, As concentration in maternal serum was significantly associated with the risk of preterm birth, which was more evident in women with a history of child marriage. As has been well studied for its impact on adverse birth outcomes, including preterm birth . As expoOur study quantitatively analyzed and thoroughly illustrated the contribution of marriage age on the risk of preterm birth by a nonlinear statistical method, and identified 18 years old as the optimal minimum marriage age with respect to risk of preterm birth. Child marriage impacts metal exposure during pregnancy and mediates the hazard by altering the concentrations of these metals. Child marriage has been illegal in Bangladesh since adoption of the Child Marriage Restraint Act of 1929. However, the law is poorly enforced because of mild punishment. Furthermore, the latest Bangladesh Child Marriage Restraint Act 2017 allows marriage under 18 in “special cases,” which would be a step backwards for Bangladesh and may result in an even higher rate of child marriage. More than half of girls from the poorest families in the developing world are married as children. Several qualitative studies have reported that adolescent mothers have a higher likelihood of spontaneous abortion, preterm birth, fetal death, and infant death –29. Our To assess the proportion of preterm birth that could be potentially prevented if risk factors were removed, the population attributable risk percentage (PAR%) was calculated for each important risk factor. Child marriage had 3.18 times higher risk  of preterm birth, and the estimated PAR% was 54.23% . Therefore, it can be seen that reducing child marriage in the society can improve most of the preterm births. In addition, candidate metals found in our study also showed significant PAR%, including As: PAR% = 21.02% , Zn: −30.24% , and Sr: −19.19%  for the first trimester and Ba: PAR% = 27.31%  for the second trimester (Appendix Table This study had some limitations. First, because each metal has a unique distribution in the organs and circulatory system, this study only tested metal concentrations in the serum, which may not be a suitable biomarker for the internal exposure of all metals . For exaThis study identified four maternal serum metal biomarkers that are jointly associated with the risk of preterm birth at crucial exposure windows during pregnancy, and jointly mediate about one-third of the risk effect of child marriage. This finding suggests that child marriage may be a modifiable factor that affects premature birth, providing support for promoting later marriage age to protect maternal-child health.Supplement Table R1


Mothers with gestational diabetes are at increased risk of giving birth by caesarean section. A standardised assessment method may help to guide in recommendations in planning caesarean birth. We analysed 203 women with gestational diabetes managed in a single centre and developed an aggregate heuristic risk score. Among 155 women who had not had a previous caesarean birth, five risk factors  were found associated with primary caesarean birth. Risk of primary caesarean birth in low‐risk women (score 0–1) was 13.8%, medium‐risk (score 2–3) 24.5% and high risk (score ≥ 4) 66.7%. The area under the receiver operating characteristic (AUROC) for primary caesarean birth prediction is 0.726 ± 0.003. Machine learning models were then deployed on 97 patients to explore the role of temporal blood glucose in predicting caesarean birth, achieving an AUROC of 0.857 ± 0.008. In conclusion, Oxford caesarean prediction score could help clinicians counselling women with gestational diabetes about their individual risk of primary caesarean birth. Temporal blood glucose measurements may improve the prediction subject to further validation. GDM is The most common adverse effect of GDM on pregnancy is accelerated foetal growth. High blood glucose stimulates the foetal pancreas to release insulin. In the foetus, insulin acts as a growth promoting hormone. The increased perinatal risks associated with GDM include emergency caesarean birth (ECB), instrumental delivery, shoulder dystocia, and birth trauma for the baby and perineal trauma for the mother. Some of these complications could potentially be avoided through either planned elective caesarean birth (PCB), or induction of labour at an earlier gestation before the baby gets too large .Unfortunately, there is no robust clinical standard to enable clinicians to confidently counsel women with GDM about their individual risk of emergency caesarean section or other complications.Guidance from the UK's National Institute for Health and Care Excellence (NICE) recommends all mothers with diabetes in pregnancy to be counselled in the third trimester (between 27 weeks and 40 weeks of pregnancy) about the mode and time of delivery . HoweverA caesarean prediction score table could be helpful to allocate healthcare resources and reduce the rate of ECB. The only model currently proposed to do this is from Thailand and has not been validated outside that setting . The HAPThroughout pregnancy, women with GDM usually perform multiple capillary blood glucose tests per day to guide diabetes management. Whilst blood glucose levels are not traditionally used in clinical algorithms to recommend the mode of delivery, the advent of digital blood glucose monitoring creates opportunities for applying machine learning and other advanced signal processing methods to determine if blood glucose data can aid mode of delivery prediction.In this paper, we address an identified clinical need for the prediction of caesarean birth, which could be used when clinicians are counselling women about their birth options . We demonstrate proof of concept for a new standardised assessment to predict caesarean birth in mothers with GDM. The aims of this paper are to (1) develop a caesarean prediction score for caesarean birth in women with GDM based on routinely collected electronic health records (EHR) to support birth planning, (2) use data‐driven machine learning models to evaluate whether prediction of caesarean birth can be improved by using EHR and temporal blood glucose measurements.2In the UK, women with GDM who have had a previous caesarean birth are offered the choice of a planned caesarean birth (PCB) or spontaneous vaginal delivery (SVD). If they have developed clinical complications, such as a large baby or breech position, PCB may be recommended. However, in many countries, every woman with a previous caesarean will be offered a PCB, or alternatively, women can individually choose to opt for a PCB. Thus, following clinical recommendations, we decided first to develop a caesarean prediction score for patients who have not previously had a caesarean birth. Then, for exploratory analysis using machine learning, we have included all patients with or without previous caesarean birth to investigate the role of blood glucose in caesarean birth prediction.2.1Inclusion and exclusion: The proposed Oxford Caesarean Prediction Score was developed using a cohort of 203 patients who were enrolled in the TREAT‐GDm randomised controlled trial at the Oxford University Hospitals NHS Trust between September 2013 and June 2015. This was a single‐centre, individually randomised controlled trial. In this trial, temporal blood glucose measurements were collected by the home glucose management and monitoring system, GDm‐Health , developWithin this cohort, as shown in Figure 2.2Clinical literature suggests that the main risk factors for PCB are breech presentation and previous caesarean birth, whereas the main risk factors for ECB are foetal distress in labour, breech presentation and size mismatch between the mother's pelvis and the baby's head .After considering the risk factors of ECB discussed in the introduction and the electronic health record (EHR) data collected in the TREAT‐GDm study, the following dependent factors were included in model development: age at the beginning of pregnancy, parity (number of previous births), ethnicity, glycated haemoglobin (HbA1c) prior to confirmation of GDM, weight, height, gestational days at recruitment and subsequent clinical visits, medication type, blood pressure (diastolic and systolic), oral glucose tolerance test results , and previous caesarean birth events.To customise a caesarean prediction score, in model one, EHR features were changed from continuous to categorical data, and a group of engineered features were generated based on clinical literature. The threshold of blood pressure in pregnancy is based on a vital signs study at Oxford University Hospitals . The hypIn model two, training and testing data in the model include routinely collected EHR data , blood glucose measurements collected through GDm‐Health, and engineered blood glucose features. Due to the limited number of patients in our data, we engineered blood glucose features instead of using raw daily blood glucose readings. The moving average method was used to deal with missing values. During the Treat‐GDm clinical trial, patients have the option to take up to six blood glucose tests every day. These readings were tagged as before‐ or after‐ breakfast, lunch and dinner. “Mean32less” and “Mean3336” are the mean blood glucose of all six‐tag readings at or before 32 weeks of pregnancy and between 33 and 36 weeks of pregnancy.We engineered two groups of engineered features based on the frequency and importance of the fasting (before‐breakfast) blood glucose reading. “BBWeek 1–6” are six weekly‐average fasting blood glucose values before the last blood glucose measurements. “BBW1ROI ‐ BBW6ROI” are the weekly average of out‐of‐threshold fasting blood glucose readings. ROI stands for the region of interest, in our case, the region beyond the normal blood glucose range. These ROI features were engineered to represent the cumulative effect of excessive blood glucose.2.3There are two modelling stages in the development process.Model one is an aggregate caesarean prediction score for the prediction of primary caesarean birth for mothers without previous caesarean. Training and testing data are physiological measurements already recorded in the TREAT‐GDm study and in routine practice when a patient is being monitored in hospital settings.Firstly we carried out a histogram observation and tests of homogeneity of variances using Levene tests on all the continuous dependent factors before converting them into categorical features. Continuous factors that were shortlisted by using chi‐square tests were then changed into categorical features based on clinical definitions (if available) or observed distributions, as defined in Table p‐value in the Chi‐square tests between the categorised risk factors and the binary delivery outcome, namely caesarean section or vaginal birth, needed to be smaller than 0.2 to be included in the final model.Secondly, a generalised linear logistic regression model with a backward stepwise conditional method was applied. The condition used in the backward stepwise was that the Thirdly, a caesarean prediction score table was generated based on the coefficients estimated in the logistic regression model. A score was allocated to each risk factor, with the magnitude of the score reflecting how extremely the parameter varies from the norm. The area under the curve (AUROC) was used to evaluate the performance of the prediction.Model two focused on using data‐driven machine learning approaches to predict the delivery mode. The machine learning models tested include a generalised linear regression model (GLM), a support vector machine (SVM), a random forest (RF), and ensemble boosting models, including AdaBoost, GentleBoost, LogitBoost (the best performance of these three models was reported). The training and testing pipeline of machine learning models is shown in Table Data downsampling was performed to address unbalanced data (in a ratio of 3:1 for non‐CB: CB) before model training. Model performance was assessed using the leave‐one‐out method. To account for the relatively small dataset, the leave‐one‐out method was repeated ten times to achieve a reliable measure of model performance. The area under ROC curve (AUROC), sensitivity and specificity were reported to evaluate the performance of models.3In model one, 155 patients were included in the development of a caesarean prediction score for women without previous caesarean birth. Among them, 120 delivered under mode one (SVD and assisted delivery) and 35 patients delivered under mode two (either planned or emergency caesarean).p < 0.05 indicates a significant correlation, and p < 0.2 is used for shortlisted risk factors.As explained in Table There were six risk factors shortlisted , 41,797 readings were included in the model training and evaluation. Among the valid readings, 19.7% were collected before breakfast, 16.3% after breakfast, 15.9% before lunch, 15.3% after lunch, 16.7 before dinner and 16.2% after dinner. Feature selection results, listed under groups of ‘EHR features’ and ‘BG features’ were reported in Table Model performance based on AUROC, sensitivity and specificity was reported in Table Results suggest that (1) there is a potential to generate a robust and accurate risk score table on delivery mode for expecting mothers with GDM, including patients with previous caesarean birth, (2) based on the ranking of feature importance in all ML models, blood glucose plays a significant role in delivery mode prediction, (3) based on the results of ML models, we need a larger dataset to allow boosting methods and tree methods to outperform GLM, as current boosting and tree models are overfitted.4This paper provides a proof of concept that prediction of caesarean birth can be done using a caesarean prediction score for mothers with GDM, and that inclusion of engineered blood glucose features can improve model performance. We propose a pragmatic approach, with an emphasis on system‐wide standardisation and the use of physiological parameters that are routinely measured in NHS hospitals and prehospital care. We developed one clinically‐plausible standardised caesarean prediction score chart, in line with the current NICE guidelines for caesarean prediction, then used data‐driven machine learning models that incorporate temporal blood glucose data, to explore the association between diabetes and delivery mode.One main challenge of providing an assessment of caesarean birth is understanding the reasons for large variations in caesarean rates in maternity clinics in the UK and worldwide. Among the UK NHS Trust hospitals, the rates of caesarean section for general maternity clinics are ranges from 13.6% to 31.9%  This demBased on discussions with clinicians, we suggest the differences in caesarean birth rate in the UK are caused by the variation of interpretation of the NICE guidelines, such as intrapartum care provision, advice given to mothers, and patient demographics. For women with an indication for caesarean birth, for example, breech, personal request, there is typically no ambiguity in clinical decision‐making for delivery mode. However, there is a lack of standard guidelines for the majority of mothers who do not have an absolute indication for caesarean birth. Clinical equipoise is most marked in women who have not had a previous caesarean section. This is why we developed the caesarean prediction score in model one, to address clinician's need for further information to inform decision making. The ultimate goal is to reduce the proportion of women undergoing ECB.The strengths of this study are the use of NICE‐guided management of diabetes in pregnancy, and use of the international WHO/IADPSG thresholds for GDM diagnosis. Whilst this is a secondary analysis of data from a clinical trial, the data were collected under “real‐life” conditions in a busy maternity diabetes service. We considered a range of clinical and non‐clinical outcomes, important for comprehensively evaluating the potential benefits of a caesarean prediction score system. We also present the first risk score table for caesarean birth in the UK cohort. We assessed the feasibility of using a caesarean prediction score that was previously developed based on a Thailand cohort to the UK cohort. The differences in model performance, as shown in Figure The study also has limitations. Our data set was relatively small and we did not have an external validation set. Therefore, we cannot comment on the performance of our Oxford caesarean prediction score table in the other UK or international cohorts, nor on the overall false‐positive rate, sensitivity or specificity needed when considering new clinical prediction tools. Another limitation is that we did not develop a caesarean prediction table using temporal blood glucose (BG) measurements. Due to the data size, the machine learning models in model two only included BG measurements before breakfast. To include features for other BG time points, and for including engineered features, we need a larger dataset. Another limitation is that we have combined delivery modes SVD, vacuum, and forceps in the same delivery mode group to distinguish from caesarean birth. This grouping method introduces heterogeneity within the group. The distribution and the variation of delivery modes were observed in our study, as shown in Figure In future studies, we would like to carry out modelling analysis on a larger patient cohort to confirm the association between blood glucose profiles during pregnancy and the likelihood of caesarean birth, and develop a caesarean prediction score for both mothers with or without previous caesarean section. A comprehensive table can assist clinic decision on caesarean planning, and advise the roles of diabetes and its management in blood glucose and medication, standardise the assessment of caesarean birth, reduce the amount of ECB, and thereby improve the quality of care for mothers with GDM.L.M. is supported by the NIHR Oxford Biomedical Research Centre and is a part‐time employee of Sensyne Health plc.This work was funded by the Royal Academy of Engineering (KHDMM280122‐001), Daphne Jackson Trust, Oxford John Fell Fund (0011028), Wellcome Trust (217650/Z/19/Z). The research was supported by the National Institute for Health Research (NIHR) Oxford Biomedical Research Centre (BRC). The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health.