Preterm birth (PTB) is defined as any delivery occurring before the 37th week of pregnancy. Medical evidence shows that a woman’s own birth history and her family’s reproductive patterns are factors in her current pregnancy risk. While the reasons for early delivery are often complex, a history of PTB in a close female relative suggests a potential, inherited susceptibility. Recognizing this connection allows healthcare providers to implement specialized monitoring and management strategies to support a full-term pregnancy.
The Inherited Tendency for Preterm Birth
A direct familial link exists: having a mother or a sister who delivered prematurely increases a woman’s own chances of experiencing a preterm birth. Studies indicate that women who were themselves born preterm have an elevated risk, with odds of delivering early 1.4 to 1.6 times higher than those born at term. This tendency is primarily passed down through the female line, pointing toward a maternal genetic contribution.
The genetic component of preterm birth is estimated to account for 25% to 40% of the variation in gestational duration. The mechanism is thought to involve genes that influence the timing of labor onset, possibly by affecting the body’s inflammatory response or the structural integrity of the uterus and cervix. This risk is elevated if the preterm history comes from the mother or maternal half-sister, but not from the father’s side of the family.
Other Significant Maternal Risk Factors
While family history establishes a baseline risk, many other independent factors in the current pregnancy can heighten the likelihood of an early delivery. The strongest predictor is a previous spontaneous preterm birth in the woman herself, which significantly increases the chance of recurrence. Also, conceiving less than 18 months after a previous delivery elevates the risk, as the mother’s body may not have sufficient time to recover.
Health and Structural Factors
Current maternal health conditions play a large part, including chronic hypertension, preeclampsia, and diabetes. Structural issues, such as a short cervix or uterine anomalies, can prevent the uterus from maintaining the pregnancy to term. Infections during pregnancy, particularly urinary tract infections (UTIs) or bacterial vaginosis, can trigger the inflammatory cascade that leads to premature labor.
Lifestyle Factors
Lifestyle choices also contribute, with smoking, substance use, and high levels of chronic stress all linked to an increased risk of preterm delivery. The mother’s pre-pregnancy weight status, being either underweight or overweight, is also a consideration. These factors are independent of the inherited risk and are the focus of prevention efforts during prenatal care.
Proactive Medical Management and Monitoring
For pregnancies identified as high-risk, specialized prenatal care is initiated to monitor and mitigate the risk. A standard screening tool is the serial transvaginal ultrasound, which measures the length of the cervix, typically between 16 and 24 weeks of gestation. A short cervical length is a strong indicator of impending spontaneous preterm birth and prompts immediate intervention.
One of the most effective preventative treatments is progesterone therapy, often prescribed to women with a history of spontaneous preterm birth. Progesterone, administered via injection or daily vaginal suppository, can reduce the risk of a recurrent preterm birth by approximately 30%. This hormone helps quiet the uterine muscle and maintain the cervical structure.
In cases where a short cervix is detected early or a woman has a history of very early deliveries, a surgical procedure called a cerclage may be recommended. A cerclage involves placing a strong stitch around the cervix to reinforce and keep it closed. If a preterm delivery becomes imminent, antenatal corticosteroids are administered to rapidly mature the baby’s lungs, and magnesium sulfate is given for neuroprotection if delivery is expected before 32 weeks.