Diversity of the Vaginal Microbiome Correlates With Preterm Birth

Abstract

Reproductive tract infection is a major initiator of preterm birth (PTB). The objective of this prospective cohort study of 88 participants was to determine whether PTB correlates with the vaginal microbiome during pregnancy. Total DNA was purified from posterior vaginal fornix swabs during gestation. The 16S ribosomal RNA gene was amplified using polymerase chain reaction primers, followed by chain-termination sequencing. Bacteria were identified by comparing contig consensus sequences with the Ribosomal Database Project. Dichotomous responses were summarized via proportions and continuous variables via means ± standard deviation. Mean Shannon Diversity index differed by Welch t test (P = .00016) between caucasians with PTB and term gestation. Species diversity was greatest among African Americans (P = .0045). Change in microbiome/Lactobacillus content and presence of putative novel/noxious bacteria did not correlate with PTB. We conclude that uncultured vaginal bacteria play an important role in PTB and race/ethnicity and sampling location are important determinants of the vaginal microbiome.

Temporal and spatial variation of the human microbiota during pregnancy

“…4B) relationships with preterm birth. This finding is consistent with previous associations between either high-diversity vaginal communities (16) or bacterial vaginosis (12,13) and increased risk for preterm birth. Of note, if we had collected specimens less frequently than weekly, we would have missed a number of excursions to CST 4 and hence would have been hindered in associating this state with preterm birth.…”

“…Two longitudinal studies (16,19) and two cross-sectional studies (14, 15) also used culture-independent methods to characterize vaginal communities sampled from one or more trimesters. In aggregate their findings suggested that the vaginal microbiota during healthy pregnancy mostly resembles the nonpregnant microbiota, but with an even higher prevalence of Lactobacillus species.…”

“…Several studies have examined the vaginal microbiota during pregnancy using cultivation-independent techniques (14)(15)(16)(17)(18)(19). Collectively, these studies found the vaginal communities of pregnant women to be dominated by Lactobacillus species and characterized by lower richness and diversity than in nonpregnant women but with higher stability.…”

“…Collectively, these studies found the vaginal communities of pregnant women to be dominated by Lactobacillus species and characterized by lower richness and diversity than in nonpregnant women but with higher stability. Of the two studies that evaluated pregnancy outcomes, one found preterm birth to be linked with higher intracommunity (alpha) diversity in the vagina (16), but the other found no significant association between preterm birth and any specific community type or microbial taxon (17).…”

13: Cervical microbiota in women with preterm pre labor rupture of membranes

“…On the other hand, Hyman et al has shown that lower genital tract microbiota in Caucasian women differs between those who delivered preterm and at term [24].…”