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    Vaginal microbiome may predict preterm birth


    Results of a case control study conducted by researchers from Stanford University show that the microorganisms on and in a woman’s reproductive tract—the microbiome—may impact her risk of preterm birth. The findings, published in The Proceedings of the National Academy of Sciences, have “important clinical implications” for predicting preterm labor and understanding how alterations in the microbiome after delivery impact maternal health, say the authors.

    Recommended: Progress and prospects for preterm birth

    The investigators took weekly samples of microorganisms from the teeth and gums, saliva, reproductive tract, and stool from 49 women during pregnancy and monthly after birth. Fifteen of the women delivered preterm. More than 4,000 samples were analyzed, using linear mixed-effects modeling, medoid-based clustering, and Markov chain modeling. The goal was to characterize weekly variation in the vaginal, gut, and oral microbiota during and after pregnancy.

    The microbiota at each of the anatomical sites remained remarkably stable during pregnancy (P<0.05 for trends over time). Prevalence of Lactobacillus-poor vaginal community state type (CST 4) was inversely correlated with gestational age at delivery (P=0.0039). Risk of preterm birth was higher in women with CST 4 plus an abundance of Gardnerella or Ureaplasma. That finding was validated with a set of 246 vaginal specimens from 9 women (4 of whom delivered preterm).

    After delivery, most women had alterations in their vaginal microbiome characterized by a decrease in Lactobacillus species and an increase in diverse anaerobes such as Peptoniphilus, Prevotella, and Anaerococcus species. The alterations were not associated with gestational age at delivery and persisted for up to 1 year.

    Given the overlap between communities sampled early and late in pregnancy at all body sites, the authors said, “the progression of pregnancy is not associated with a dramatic remodeling of the diversity and composition of a woman’s indigenous microbiota.” After birth, the authors noted, the vaginal microbiome becomes more similar to the one in the gut. The impact of that shift is unknown, but the investigators hypothesize that it may affect a subsequent pregnancy if conception occurs soon after delivery because a short interpregnancy interval is associated with an increased risk of preterm birth. 

    NEXT: Do some types of work impact the chances of becoming pregnant?

    Judith M. Orvos, ELS
    Judith M. Orvos, ELS, is a a BELS-certified medical writer and editor and an editorial consultant for Contemporary OB/GYN.
    Miranda Hester
    Ms. Hester is Content Specialist with Contemporary OB/GYN and Contemporary Pediatrics.


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