The vaginal bacteriome of pregnant Rwandan and Kenyan women, unique regional genera associations with preterm birth

Preterm birth, defined as gestational duration less than 37 weeks, often results in lifelong adverse health impacts for children. East African women have some of the highest rates of preterm birth globally. Previous studies have suggested that changes in the vaginal bacteriome may be associated with increased risk for preterm birth. The absence of Lactobacilli dominated vaginal flora and increased alpha and beta diversity have been associated with preterm birth in other contexts, primarily from US-based studies with African-American women. Few studies have been conducted with women from sub-Saharan Africa to assess whether vaginal bacteriome are associated with preterm birth risk. Using a longitudinal cohort study design, we recruited two groups of women from Kisumu, Kenya and Kigali, Rwanda in the first or second trimesters of pregnancy as confirmed via abdominal ultrasound. At the same time as abdominal ultrasound, vaginal bacteriome samples were collected and women were interviewed about sociodemographic and health backgrounds. Women were followed until delivery and gestational age was calculated and newborn birthweight determined. Sequencing of the 16S rRNA was subsequently conducted to assess specific vaginal flora and alpha and beta diversity by country and in relation to the preterm outcome. Pearson and Spearman correlation and heatmap of taxa associated with preterm versus term birth and by country of origin were calculated. Differences in genera abundance were assessed as well as metrics of alpha and beta diversity between Kenyan and Rwandan samples. We included 118 women each from Kenya and Rwanda finding significant differences in beta diversity between countries but no association between alpha and beta diversity and preterm birth. We found differences in flora associated with preterm birth by country, although for both Kenya and Rwanda, higher counts of Lactobacilli were associated with term delivery. Different bacteriome determined preterm birth status by country with Staphylococcus and Fannyhessea significant in Rwanda but Gardnerella more common among Kenyan women. This is the first study that demonstrates there may be regional differences among East African women in the types of vaginal flora that are associated with preterm birth.