Vaginal microbiome in early pregnancy and subsequent risk of spontaneous preterm birth: a case-control studyOriginal paper
Karen Pendergrass is a microbiome researcher specializing in microbiome-targeted interventions (MBTIs). She systematically analyzes scientific literature to identify microbial patterns, develop hypotheses, and validate interventions. As the founder of the Microbiome Signatures Database, she bridges microbiome research with clinical practice. In 2012, based on her own investigative research, she became the first documented case of FMT for Celiac Disease, four years before the first published case study.
Read MoreWhat was studied?
This case-control study asked whether the early-pregnancy vaginal microbiome differs between women who later delivered preterm and those who delivered at term. Researchers sequenced the V4 region of the 16S rRNA gene from vaginal swabs self-collected in early pregnancy. They compared relative abundance of bacterial taxa and oligotypes. They also assigned each woman to a vaginal community state type (CST). The design separated early preterm birth (before 34 weeks) from late preterm birth (34 to 36 weeks). The authors describe it as the largest study of its kind.
Who was studied?
The cohort was 450 pregnant women from the 3D birth cohort in Quebec, Canada. Ninety-four had spontaneous preterm birth, split into 17 early (before 34 weeks) and 77 late (34 to 36 weeks) cases. The remaining 356 women were controls who delivered at term, at 37 weeks or later. Swabs were self-collected during early pregnancy. This was a human, community-based nested case-control analysis.
What were the most important findings?
Four taxa tracked with lower risk of early preterm birth but not late preterm birth. These were Lactobacillus gasseri/johnsonii (coefficient -5.36), Lactobacillus crispatus/acidophilus (-4.58), Lactobacillus iners/Ralstonia solanacearum (-3.98), and Bifidobacterium longum/breve (-8.84). Six community state types emerged, four dominated by Lactobacillus, one rich in bacterial vaginosis bacteria (Gardnerella vaginalis, Atopobium vaginae, Veillonellaceae), and one lacking Lactobacillus dominance. The bacterial vaginosis type raised early preterm risk over fourfold (odds ratio 4.22, 95% CI 1.24 to 24.85) versus the non-Lactobacillus type. Late preterm birth showed no such association.
What are the greatest implications of this study?
The findings suggest specific vaginal bacteria relate to timing of preterm birth, with effects concentrated in early preterm birth before 34 weeks. Certain Lactobacillus and Bifidobacterium species associated with protection. A bacterial vaginosis community pattern associated with higher early preterm risk. These are associations from swabs taken in early pregnancy, not proof of cause. The distinction between early and late preterm birth matters, because signals present for early cases did not extend to late cases.