Researchers recently discovered the bacterial communities present in a woman's vagina during pregnancy may increase risks of premature labor. Pregnant women with decreased abundances of Lactobacillus strains in the vaginal microbiome experienced increased rates of premature birth compared to women with vaginal microbiomes enriched in Lactobacilli.
In addition to decreased abundances of Lactobacillus strains, the study also indicated higher levels of Ureaplasma and Gardnerella were tied to greater risks of premature labor.
If these results can be confirmed in larger studies, sequencing the vaginal microbiome throughout pregnancy might help determine women at high risk for preterm labor. Doctors may be able to use the vaginal microbiome as a diagnostic marker or tool to identify pregnancies that may have an increased risk of premature labor.
Preterm labor, defined as birth prior to 37 weeks, happens in nearly 11 percent of pregnancies internationally.
Finding the cause of Premature Birth
Researchers are not sure if the shifts in the vaginal microbiome are the only contributing cause for premature birth. However, they do believe that contributing factors for premature birth might also cause shifts within the vaginal microbiome.
Throughout the study, researchers observed the vaginal bacterial communities in 49 pregnant women aged 18 years and older weekly until after childbirth. The scientists sequenced the women's vaginas, gums, stool, and saliva. In this study, fifteen women experienced premature births.
Most women experienced a significant shift within the vaginal microbiome bacterial populations at the time of delivery. A wide range of bacteria replaced Lactobacillus strains, which were found in decreased abundances. This shift was observed for up to one year later in some women.
Although researchers are unsure how this shift affects the mother's health or how it actually happens, it is possible that shifts of bacteria communities in the vagina after childbirth might affect the risk of premature labor in a following pregnancy if conception occurs shortly after the previous delivery.
DiGiulio, D.B. et al, Temporal and spatial variation of the human microbiota during pregnancy. PNAS. (2015). 112 (35) 11060-11065; doi: 10.1073/pnas.1502875112