There are many different factors that determine the exact length of time it takes before labor begins, but a pregnancy that lasts approximately 40 weeks is considered normal, safe, and healthy. When a woman goes into labor before 37 weeks after her last period, which occurs in about 12% of US births, it is known as preterm labor. Depending on the health of the woman, the baby, and the reason for the preterm labor birth, the newborn may be at greater risk for health issues and other problems.
There are many different preterm labor birth causes, and typically it isn’t one single factor that causes preterm labor, but a number of risk factors acting together. The medical community has identified several characteristics of the pregnancy, mother, and fetus that can increase the chance of preterm labor, and when many of these risk factors are present, there will likely be a preterm birth. It’s important to understand these causes in order to prevent premature labor, because preterm labor birth can cause a number of issues for children.
Early Rupture of Amniotic Membranes
One of the leading preterm labor birth causes is premature draining of the amniotic sac. Almost one in three premature births is preceded by a premature loss of amniotic fluid. Once this fluid has flowed out of the uterus, it’s very important that the baby is delivered soon after.
There are a number of different things that can cause the amniotic membranes to rupture earlier than expected. For example, if the uterus is too large or if there is too much amniotic fluid, the amniotic membranes may have less strength and cohesion. Those who are having a multiple pregnancy, such as twins or triplets, often have a very large amount of amniotic fluid in their uterus, and they also have a higher risk of the membranes rupturing at an early stage. Pregnant women who are underweight or overweight are more likely to experience early loss of amniotic fluid as well.
Hypertension and Bleeding Disorders
Having very high blood pressure during pregnancy is recognized as a significant risk factor and one of the most common preterm labor birth causes. Experts do not know exactly why hypertensive conditions increase the chance or cause premature birth, but the evidence shows that chronic hypertension and preeclampsia can increase the chance of a premature birth. In addition, obesity, smoking, stress, and other causes of high blood pressure have a significant effect on when the birth occurs.
Bleeding disorders like hemophilia and other disorders such as anemia are also linked to preterm labor. Additionally, there is a strong correlation between maternal diabetes and preterm labor.
Problems With Cervix or Uterus
Sometimes there is an issue with the mother’s cervix or uterus, and this reduces the cervix’s ability to stay closed and prevent a premature birth. If the cervix or uterus is too large or if the weight of the fetus is distributed in an irregular way, it can also cause birth before 40 weeks of pregnancy.
Infections and STIs are well-documented as preterm labor birth causes. Infections caused by chlamydia, gonorrhea, syphilis, and trichomoniasis are especially related to premature labor, and research suggests that these infections affect the strength and ability of the cervix to remain closed and support the developing fetus.
Other Preterm Labor Birth Causes
There are a number of other conditions that can increase the risk or cause a preterm birth. Some of these risk factors include vaginal bleeding, no prenatal care, smoking and drinking, and in vitro fertilization. In some circumstances, the health of the baby or mother is at risk, and the preterm labor is induced by the medical staff.