Researchers reported on Mar. 15 that changes in the vaginal microbiome during pregnancy may influence inflammation and the risk of preterm birth, according to a review published in npj Biofilms and Microbiomes. The review points to new microbiome-based therapies that could improve health outcomes for mothers and infants.
Preterm birth, defined as delivery before 37 weeks of gestation, remains a leading cause of neonatal illness and infant death worldwide. Estimates suggest about 13.4 million premature births occurred globally in 2020, representing roughly 9.9% of all deliveries. Despite advances in obstetric care, rates of preterm birth have not significantly changed in many regions, with marked disparities observed among different populations.
The review highlights evidence that a vaginal environment dominated by Lactobacillus bacteria is commonly linked to immune tolerance during pregnancy, while disruptions—known as dysbiosis—are associated with harmful inflammatory responses. "Lactobacillus crispatus produces lactic acid that maintains a highly acidic vaginal environment (pH 3.5–4.5). This acidic environment reinforces the epithelial barrier and suppresses inflammatory signaling," the authors said.
Disparities in microbiome composition were also discussed, particularly among women of African and Hispanic ancestry who more often have higher levels of Lactobacillus iners—a species considered less stable than L. crispatus and potentially more prone to shifts toward dysbiosis. However, the review notes that not all non-Lactobacillus-dominated communities are harmful; some may remain stable without causing inflammation.
Current treatments for bacterial vaginosis using antibiotics initially clear infection in most cases but often fail to restore protective bacteria, leading to high recurrence rates within a year. New therapies under investigation include live biotherapeutic products designed to reintroduce beneficial microbes directly into the vaginal environment.
The authors emphasized the need for large-scale studies involving diverse populations to ensure future interventions are effective across different groups: "Research remains limited in many marginalized populations. Large, longitudinal studies involving diverse ancestral groups will be essential to translate microbiome discoveries into equitable and effective clinical interventions."
