Role of Age in Mediating the Association Between the Vaginal Microbiota and Preterm Birth

The vaginal microbiota plays a crucial role in vaginal health and pregnancy outcomes. However, the influence of maternal characteristics, especially age, on the relationship between the vaginal microbiota and preterm birth is poorly understood. This study quantifies the effects of race, maternal age, and gestational age on vaginal microbiota composition. Our results demonstrate stronger associations between preterm birth and a less optimal vaginal microbiota in White and Asian women compared to Black or African American women. The microbiota difference between preterm and term births was more pronounced in older reproductive-age women, with Lactobacillus species increasing with age only in term births. Additionally, lower alpha diversity was observed in term pregnancies compared to preterm during both early and late pregnancy, particularly in women aged above 25 years. These findings highlight the mediating role of age in the relationship between the vaginal microbiota and preterm birth.