Race, the Vaginal Microbiome, and Spontaneous Preterm Birth

Abstract

Approximately 10% of all pregnancies in the United States end in preterm birth, and over 14% of pregnancies end in preterm birth among Black women. Knowledge on the associations between vaginal microbiome and preterm birth is important for understanding the potential cause and assessing risk of preterm birth.

The Vaginal Microbiota in Early Pregnancy Identifies a Subset of Women at Risk for Early Preterm Prelabor Rupture of Membranes and Preterm Birth

“…Investigations have been conducted in populations of American (Asian, African, Caucasian, Hispanic) 29-34, 37,42,43,50,59 , Canadian (Arabic, Asian, African, Caucasian) 39,40 , European (Asian, African, Caucasian) 35,36,38,44,51,55 , Brazilian 41,45 , Peruvian 47 , Nigerian 54 , Indian 53 , Chinese 57,60 , Korean 46,48 , Japanese 58 , and Thai (Karen, Burman) 52 women. Although populations of women worldwide have the same bacterial taxa in their vaginal microbiota [61][62][63][64]75 , the relative abundances of these taxa can vary between and within populations, including by ethnicity 30,42,43,51,59,61-64,76−78 . It is therefore likely that associations between the structure of the vaginal microbiota and sPTB will be observed in some populations and/or ethnicities, but not in others 34,36,42,43,51,59 , and that this will contribute to the inconsistencies in results among studies.…”

“…It is therefore likely that associations between the structure of the vaginal microbiota and sPTB will be observed in some populations and/or ethnicities, but not in others 34,36,42,43,51,59 , and that this will contribute to the inconsistencies in results among studies. Third, there has been variation among the longitudinal studies in the distributions of gestational age at sampling between cases and controls 29,31,34,43,44,52,59 . Given that gestational age at sampling has a pronounced effect on vaginal microbiota pro les in pregnancy [65][66][67]78 , it is critical that the distributions of gestational age at sampling between women delivering preterm versus at term are similar.…”

“…Fourth, there has been variation among studies in how sPTB has been de ned. It has been variably de ned as delivery < 37 weeks 37,45,52−54 , non-indicated delivery < 33 41 , <34 29,55 , <35 33 , or < 37 30,32,39,40,43,44,47,48,50,51,55,59 weeks, non-indicated delivery < 34 or < 37 weeks excluding PPROM 35 , PTL with delivery < 37 weeks 36,58 , or sPTB with cervical dilation and/or PPROM < 37 weeks 42 . Furthermore, most prior studies have considered cases of sPTB uniformly 29-32, 34,37, 39-44,47,48, 50-55,59 , without subclassi cation into those deriving from PTL and those due to PPROM.…”

“…Although populations of women worldwide have the same bacterial taxa in their vaginal microbiota [61][62][63][64]75 , the relative abundances of these taxa can vary between and within populations, including by ethnicity 30,42,43,51,59,61-64,76−78 . It is therefore likely that associations between the structure of the vaginal microbiota and sPTB will be observed in some populations and/or ethnicities, but not in others 34,36,42,43,51,59 , and that this will contribute to the inconsistencies in results among studies. Third, there has been variation among the longitudinal studies in the distributions of gestational age at sampling between cases and controls 29,31,34,43,44,52,59 .…”

“…In this study, the presence of only one bacterium was negatively associated with the incidence of early PPROM -Lactobacillus crispatus. In prior molecular investigations of the vaginal microbiota and sPTB, Lactobacillus has been consistently associated with delivery at term 31,[34][35][36]41,43,44,48,49,[51][52][53][54]59 , and L. crispatus is hypothesized to play a protective role in the vagina both in and outside of pregnancy 34-36,43,48,66,67,69,70,133−137 . The mechanisms underlying the hypothesized protective effect of L. crispatus within the vagina include its production of lactic acid (especially D-lactic acid) 138-141 and antimicrobial compounds (e.g.…”