Study Finds Cervicovaginal Microbiota Different in Women Destined to Have Preterm Birth

In a study to be presented on Feb. 6 at 3:15 p.m. CST, at the Society for Maternal-Fetal Medicine’s annual meeting, The Pregnancy Meeting ™, in New Orleans, researchers will report that cervicovaginal (CV) microbiota differs in the late second and early third trimester in women destined to have a preterm birth.

The study tested vaginal swabs from pregnant women in the late second trimester (20-24 weeks) and early third trimester (24-28) weeks of pregnancy, and compared the CV biospecimens of women who ultimately had a preterm birth to those who had a term birth.

Using DNA obtained on those swabs, the microbial communities were characterized by community state types (CSTs) using state-of-the-art technology. CST I are dominated by Lactobacillus crispatus, traditionally considered a beneficial bacteria. CST III are dominated by Lactobacillus iners, and CST IV are dominated by anaerobic bacteria normally considered to contribute to the condition of bacterial vaginosis.

“We compared the proportion of CSTs in the women who ultimately had a preterm birth to those who had a term birth,” said Michal Elovitz, M.D. “The percent of non-CST III was significantly lower in samples from women delivering preterm than term. Notably, the differences in these microbial communities were evident in the late second trimester of pregnancy, weeks if not months prior to the preterm birth.”

Elovitz, director of the Maternal and Child Health Research Program at the Perelman School of Medicine at the University of Pennsylvania, said that further research is required to find out how these different microbial communities contribute to preterm birth. “This study is the first to report such key differences in the CV microbial communities weeks prior to preterm birth. If differences in the CV microbial communities are confirmed, then new and exciting therapeutic strategies will emerge to prevent preterm birth.”

With funding from the National Institute of Nursing Research, Elovitz confirmed that the team of researchers on this study is currently pursuing a large prospective cohort to further understand the role of CV microbial communities in preterm birth.

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A copy of the abstract is available at and below.  For interviews please contact Vicki Bendure at 202-374-9259 (cell), or Meghan Blackburn at, 540-687-5099 (office) or 859-492-6303 (cell).


The Society for Maternal-Fetal Medicine (est. 1977) is the premiere membership organization for obstetricians/gynecologists who have additional formal education and training in maternal-fetal medicine.  The society is devoted to reducing high-risk pregnancy complications by sharing expertise through continuing education to its 2,000 members on the latest pregnancy assessment and treatment methods. It also serves as an advocate for improving public policy, and expanding research funding and opportunities for maternal-fetal medicine. The group hosts an annual meeting in which groundbreaking new ideas and research in the area of maternal-fetal medicine are shared and discussed.  For more information visit

Abstract 26: The cervicovaginal microbiota is different in women destined to have a preterm birth

Authors: Michal Elovitz1, Pawel Gajer2, Jamie Bastek1, Laura Anglim1, Amy Brown1, Jacques Ravel2

1University of Pennsylvania, Maternal and Child Health Research Program; Dept OBGYN, Philadelphia, PA, 2University of Maryland School of Medicine, Institute of Genomic Sciences, Baltimore, MD

Objective: The importance of microbial communities to human health and disease is just now being revealed. For decades, the vaginal microbiota has been thought to contribute to preterm birth (PTB). However, there remains a paucity of data characterizing the cervico-vaginal (CV) microbiota in women destined to have a PTB.

Study Design: Using CV biospecimens from a prospective cohort of women at high risk for PTB, the microbiota at 20-24 weeks (V1) and at 24-28 weeks (V2) was analyzed in women who ultimately had a PTB (N=14) compared to those who had a term birth (N=32). Taxonomic assignment of 16S rRNA reads was done using Markov Chain taxonomy classifier. 128 phylotypes were identified in the 78 samples. Samples were clustered into community state types (CST) I, III and IV based on established nomenclature (Ravel et al.,PNAS 2010). CSTs I are dominated by Lactobacillus crispatus and CST III by Lactobacillus iners. Samples of CST IV lack substantial number of different Lactobacillus spp. and have anaerobic bacteria. In order to identify phylotypes whose relative abundance is significantly different between samples, 0-inflated negative binomial models were fitted to the relative abundance data of 50 phylotype that were present in at least 25% of all samples.

Results: Proportion of CSTs differed at V1 and V2 in women destined to have a PTB compared to term (Fig 1). In analyzing all samples, CST proportions were significantly different in women who had a PTB (16.7, 61.1 and 22.2%) compared to term (35.0, 31.6, 33%)(P=0.012). Percent of non-CST III was significantly higher in samples from women delivering at term than in those with PTB (68% vs. 39%, P=0.002).

Conclusion: The CV microbiota differs in the late 2nd and early 3rd trimester in women destined to have a PTB. The mechanisms by which altered microbiota promote preterm parturition require urgent investigation. Since microbiota can be manipulated through pre-and probiotics, targeting the microbiota for the prevention of PTB should become an active area of research.

Fig. 1

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