Can Probiotics Help Prevent Preterm Birth?

Preterm birth, defined as delivering a baby before 37 weeks of pregnancy, is a major global health concern and one of the leading causes of newborn illness and death. In 2020 alone, an estimated 13.4 million babies were born preterm worldwide, and complications from preterm birth were linked to nearly 1 million deaths. Babies born too early face increased risks of serious health problems, including infections, bleeding in the brain, developmental delays and long-term conditions such as cerebral palsy.

For women who have already experienced a spontaneous preterm delivery (meaning labor began naturally rather than being medically induced), the risk of having another preterm birth is significantly higher. Globally, about 30% of these women will experience a recurrence, making prevention a critical focus in maternal care.

A new study published in the American Journal of Obstetrics and Gynecology looked at whether probiotics (beneficial bacteria that support gut and immune health) could help reduce the risk of repeat preterm birth. A team of investigators focused on a specific combination of probiotic strains, including Clostridium butyricum, which may help regulate the immune system by promoting cells that support a healthy pregnancy environment.

“This study was motivated by our desire to reduce the number of children who develop long-term disabilities, especially those born extremely preterm, through appropriate obstetric interventions,” said lead investigator Satoshi Yoneda, M.D., Ph.D., an associate professor in the Department of Obstetrics and Gynecology at the University of Toyama, Japan.

The study included 315 pregnant women in Japan, all of whom had a history of spontaneous preterm delivery. Participants took a daily probiotic supplement starting early in pregnancy (between 10 and 14 weeks) and continued until late pregnancy (just before full term). Investigators then compared their outcomes with previously reported national data.

The findings were encouraging. The rate of recurrent preterm birth in this group was 14.9%, which is notably lower than the historical rate of 22.3% seen in similar populations. This suggests that probiotics may help reduce the likelihood of another early delivery.

The study also looked at more severe cases. Early preterm births (before 34 weeks) occurred in just 3.5% of participants. Among women who had previously experienced extremely early preterm birth (before 28 weeks), the recurrence rate dropped to just 1.5%. These results are especially important because earlier births are typically associated with greater health risks for the baby.

Safety is always a key concern during pregnancy, and the study found no serious adverse events linked to the probiotic use. There were also no stillbirths reported. Mild side effects were consistent with what researchers would expect in a general pregnant population, suggesting the treatment was well tolerated.

While these results are promising, it’s important to understand the study’s limitations. This was a single-arm trial, meaning all participants received the probiotic and there was no comparison group within the study itself. Instead, outcomes were compared to historical data. Because of this, investigators say more rigorous studies, such as randomized controlled trials, are needed to confirm the benefits.

Still, this research highlights a potentially simple and low-risk strategy to help reduce repeat preterm birth in high-risk women. If future studies confirm these findings, probiotics could become part of routine care for certain pregnancies.

“Probiotics containing butyrate-producing bacteria initiated in early pregnancy may help prevent preterm delivery in women with a history of or at high risk for spontaneous preterm delivery,” Yoneda concluded.