Premature birth may be linked to mother's cervicovaginal bacteria

Researchers found that the presence of certain bacteria in the cervix or vagina may affect a woman’s risk for pre-term birth, thus offering a potential target for therapy, according to findings presented recently at The Pregnancy Meeting.

"Although conventional wisdom says premature birth begins in the uterus, we decided to take an entirely new look at the problem," Michal Elovitz, MD, professor, obstetrics and gynecology at the University of Pennsylvania, said in a press release. “We are very excited to report that we did find significant differences in the microbial communities early in pregnancy in women who ultimately have a preterm birth compared to a term birth.”

Elovitz and colleagues analyzed the specimens found on vaginal swabs from 1,500 women at 16 to 20 weeks in pregnancy, then again at 20 to 24 weeks and again at 24 to 28 weeks. A smaller group of 616 women with specimens collected between 22 and 32 weeks was used as a validation cohort.

From the larger cohort, a nested case-control was performed with 80 spontaneous preterm birth (SPTB) cases and 320 term controls that were frequency-matched by race to the cases. The researchers performed16S rRNA gene analysis to characterize the composition and structure of the cervicovaginal microbiota. The effect of bacteria was quantified as the log ratio between the mean relative abundance at SPTB samples vs. term delivery samples. Log ratios were estimated using zero-inflated negative binomial models.

The researchers identified 127 phylotypes in all samples from both cohorts. They found significant associations were demonstrated between specific bacteria and SPTB: 37 bacteria were significantly associated with a decreased risk of SPTB while 13 were associated with an increased risk in the primary cohort. The associations differed between black and white women.

The validation cohort confirmed the highly significant associations between specific microbes and SPTB. Bifidobacterium species were protective against SPTB at all gestational time points while BVAB2, BVAB3 and Mobiluncus were associated with a considerable increase in risk for SPTB.

"Different bacterial species were associated with quite a dramatic increased risk of premature birth. If our study is confirmed, it could mean that targeting [cervicovaginal] bacteria may be a new therapy to prevent premature birth in the immediate future, not decades from now," Elovitz said in the release.– by Janel Miller

Reference: Elovitz, M, et al. Distinct microbiota in the cervicovaginal space are associated with spontaneous preterm birth: Findings from a large cohort and validation study. Presented at: The Pregnancy Meeting; Jan. 23-28, 2017; Las Vegas.

Disclosure: According to the release, Elovitz was able to pursue the research as co-investigator for the March of Dimes Prematurity Research Center at the University of Pennsylvania and studies funded by the NIH. Healio Family Medicine was unable to determine the other researchers’ relevant financial disclosures prior to publication.