The main categories of causes of<unk>  are<unk>  labor induction and spontaneous<unk>  labor. Risk factors The exact cause of spontaneous<unk>  is difficult to determine and it may be caused by many different factors at the same time as labor is a complex process. Four different pathways have been identified that can result in<unk>  and have considerable evidence: precocious fetal endocrine activation, uterine overdistension (placental abruption), decidual bleeding, and intrauterine inflammation or infection. Identifying women at high risk of giving birth early would enable the health services to provide specialized care for these women and their babies, for example a hospital with a special care baby unit such as a neonatal intensive care unit (NICU). In some instances, it may be possible to delay the birth. Risk scoring systems have been suggested as an approach to identify those at higher risk, however, there is no strong research in this area so it is unclear whether the use of risk scoring systems for identifying mothers would prolong pregnancy and reduce the numbers of<unk> s or not. Maternal factors Risk factor Relative risk 95% confidence interval Fetal fibronectin 4.0 2.9–5.5 Short cervical length 2.9 2.1–3.9 Prenatal Care Absent 2.9 2.8–3.0 Chlamydia 2.2 1.0–4.8 Low socio-economic status 1.9 1.7–2.2 Large or small pregnancy weight gain 1.8 1.5–2.3 Short maternal height 1.8 1.3–2.5 Periodontitis 1.6 1.1–2.3 Celiac disease 1.4 1.2–1.6 Asymptomatic bacteriuria 1.1 0.8–1.5 High or low BMI 0.96 0.66–1.4 odds ratio History of spontaneous<unk>  3.6 3.2–4.0 Bacterial vaginosis 2.2 1.5–3.1 Black ethnicity/race 2.0 1.8–2.2 Filipino ancestry 1.7 1.5–2.1 Unwanted pregnancy 1.5 1.41-1.61 Unintended pregnancy 1.31 1.09-1.58 Being single/unmarried 1.2 1.03–1.28 Percentage premature births in England and Wales 2011, by age of mother and whether single or multiple birth. Risk factors in the mother have been identified that are linked to a higher risk of a<unk> . These include age (either very young or older), high or low body mass index (BMI), length of time between pregnancies, previous spontaneous (i.e., miscarriage) or surgical abortions, unintended pregnancies, untreated or undiagnosed celiac disease, fertility difficulties, heat exposure, and genetic variables. Studies on type of work and physical activity have given conflicting results, but it is opined that stressful conditions, hard labor, and long hours are probably linked to<unk> . Obesity does not directly lead to<unk> ; however, it is associated with diabetes and hypertension which are risk factors by themselves. To some degree those individuals may have underlying conditions (i.e., uterine malformation, hypertension, diabetes) that persist. Couples who have tried more than 1 year versus those who have tried less than 1 year before achieving a spontaneous conception have an adjusted odds ratio of 1.35 (95% confidence interval 1.22-1.50) of<unk> . Pregnancies after IVF confers a greater risk of<unk>  than spontaneous conceptions after more than 1 year of trying, with an adjusted odds ratio of 1.55 (95% CI 1.30-1.85). Certain ethnicities may have a higher risk as well. For example, in the U.S. and the UK, Black women have<unk>  rates of 15–18%, more than double than that of the white population. Many Black women have higher<unk>  rates due to multiple factors but the most common is high amounts of chronic stress, which can eventually lead to premature birth. Adult chronic disease isn't always the case with premature birth in Black women, which makes the main factor of premature birth challenging to identify. Filipinos are also at high risk of premature birth, and it is believed that nearly 11–15% of Filipinos born in the U.S. (compared to other Asians at 7.6% and whites at 7.8%) are premature. Filipinos being a big risk factor is evidenced with the Philippines being the eighth-highest ranking in the world for<unk> s, the only non-African country in the top 10. This discrepancy is not seen in comparison to other Asian groups or Hispanic immigrants and remains unexplained. Genetic make-up is a factor in the causality of<unk> . Genetics has been a big factor into why Filipinos have a high risk of premature birth as the Filipinos have a large prevalence of mutations that help them be predisposed to premature births. An intra- and transgenerational increase in the risk of<unk>  delivery has been demonstrated. No single gene has been identified. Marital status is associated with risk for<unk> . A study of 25,373 pregnancies in Finland revealed that unmarried mothers had more<unk>  deliveries than married mothers (P=0.001). Pregnancy outside of marriage was associated overall with a 20% increase in total adverse outcomes, even at a time when Finland provided free maternity care. A study in Quebec of 720,586 births from 1990 to 1997 revealed less risk of<unk>  for infants with legally married mothers compared with those with common-law wed or unwed parents. Factors during pregnancy Medications during pregnancy, living conditions, air pollution, smoking, illicit drugs or alcohol, infection, or physical trauma may also cause a<unk> . Air pollution: Living in an area with a high concentration of air pollution is a major risk factor for<unk>  labor, including living near major roadways or highways where vehicle emissions are high from traffic congestion or are a route for diesel trucks that tend to emit more pollution. The use of fertility medication that stimulates the ovary to release multiple eggs and of IVF with embryo transfer of multiple embryos has been implicated as a risk factor for<unk> . Often labor has to be induced for medical reasons; such conditions include high blood pressure, pre-eclampsia, maternal diabetes, asthma, thyroid disease, and heart disease. Certain medical conditions in the pregnant mother may also increase the risk of<unk> . Some women have anatomical problems that prevent the baby from being carried to term. These include a weak or short cervix (the strongest predictor of premature birth). Women with vaginal bleeding during pregnancy are at higher risk for<unk> . While bleeding in the third trimester may be a sign of placenta previa or placental abruption—conditions that occur frequently<unk> —even earlier bleeding that is not caused by these conditions is linked to a higher<unk>  rate. Women with abnormal amounts of amniotic fluid, whether too much (polyhydramnios) or too little (oligohydramnios), are also at risk. Anxiety and depression have been linked as risk factors for<unk> . The use of tobacco, cocaine, and excessive alcohol during pregnancy increases the chance of<unk>  delivery. Tobacco is the most commonly used drug during pregnancy and contributes significantly to low birth weight delivery. Babies with birth defects are at higher risk of being born<unk> . Passive smoking and/or smoking before the pregnancy influences the probability of a<unk> . The World Health Organization published an international study in March 2014. Presence of anti-thyroid antibodies is associated with an increased risk<unk>  with an odds ratio of 1.9 and 95% confidence interval of 1.1–3.5. Intimate violence against the mother is another risk factor for<unk> . Physical trauma may case a<unk> . The Nigerian cultural method of abdominal massage has been shown to result in 19%<unk>  among women in Nigeria, plus many other adverse outcomes for the mother and baby. This ought not be confused with massage therapy conducted by a fully trained and certified/licensed massage therapist or by significant others trained to provide massage during pregnancy, which has been shown to have numerous positive results during pregnancy, including the reduction of<unk> , less depression, lower cortisol, and reduced anxiety. Infection The frequency of infection in<unk>  is inversely related to the gestational age. Mycoplasma genitalium infection is associated with increased risk of<unk> , and spontaneous abortion. Infectious microorganisms can be ascending, hematogeneous, iatrogenic by a procedure, or retrograde through the Fallopian tubes. From the deciduas they may reach the space between the amnion and chorion, the amniotic fluid, and the fetus. A chorioamnionitis also may lead to sepsis of the mother. Fetal infection is linked to<unk>  and to significant long-term handicap including cerebral palsy. It has been reported that asymptomatic colonization of the decidua occurs in up to 70% of women at term using a DNA probe suggesting that the presence of micro-organism alone may be insufficient to initiate the infectious response. As the condition is more prevalent in black women in the U.S. and the UK, it has been suggested to be an explanation for the higher rate of<unk>  in these populations. It is opined that bacterial vaginosis before or during pregnancy may affect the decidual inflammatory response that leads to<unk> . The condition known as aerobic vaginitis can be a serious risk factor for<unk>  labor; several previous studies failed to acknowledge the difference between aerobic vaginitis and bacterial vaginosis, which may explain some of the contradiction in the results. Untreated yeast infections are associated with<unk> . A review into prophylactic antibiotics (given to prevent infection) in the second and third trimester of pregnancy (13–42 weeks of pregnancy)
Preterm birth
Breech birth
Low birth weight
Multiple birth
Low Birth Weight
Stillbirth
Birth injury
Birth trauma 