The vaginal microbiota varies by self-identified ethnicity and HIV status throughout pregnancy and predicts preterm birth risk in the United Kingdom
Background  Low-diversity, Lactobacillus-dominated vaginal microbiota are associated with immune protection in pregnancy, whereas community state type (CST) IV and transitional CST III are linked to inflammation and preterm birth (PTB). Pregnant women living with HIV (PWLWH) in the UK have higher preterm birth (PTB) rates than pregnant women without HIV (PWWH). We previously demonstrated in a cohort of PWLWH from the UK HIV Preterm Birth Network (UHPBN) study, who predominantly self-identified as having a Black ethnic background, PTB occurred in association with non-optimal CSTs III and IV. It remains unclear how these associations varied by HIV status and social factors. This larger updated analysis compares vaginal microbiota composition, inflammation, and PTB outcomes across self-identified Black and White PWLWH and PWWH. Results 135 women from the UHPBN study provided second trimester vaginal samples.  Samples were available from 55 Black PWLWH, 14 Black PWWH, 15 White PWLWH, and 19 White PWWH for these analyses. Of the 12 PTBs, 10 occurred in Black PWLWH (18% PTB rate). Black pregnant women showed the highest alpha diversity, while White PWWH had the lowest. Black women and White PWLWH exhibited a higher prevalence of CSTs III and IV and lower prevalence of CST I. Among Black women, HIV status did not influence Chao1 diversity or inflammation, whereas among White women, HIV was associated with increased Chao1 (p=0.007) and higher composite inflammation (p< 0.001). In Black PWLWH, PTB was associated with CSTs III and IV. Nearly half of Black PWLWH (49%) underwent a CST transition and were more likely to transition compared to other subgroups (Adjusted odds ratio (aOR) 0.40, 95% CI 0.15–0.98; p=0.048). Overall CST change trended toward increased PTB risk (aOR 3.50, 95% CI 0.82–18.46; p=0.10); however, transitioning between CSTs III and IV was associated with increased PTB risk (aOR 7.75, 95% CI 1.57–42.75; p=0.01). Conclusions Black PWLWH had the highest PTB rates, strongly associated with non-optimal CSTs and CST transitions during the second trimester. The high prevalence of CSTs III and IV among Black women regardless of HIV status, and among White PWLWH, may reflect broader socioeconomic determinants of reproductive health.
Background  Low-diversity, Lactobacillus-dominated vaginal microbiota are associated with immune protection in pregnancy, whereas community state type (CST) IV and transitional CST III are linked to inflammation and preterm birth (PTB). Pregnant women living with HIV (PWLWH) in the UK have higher preterm birth (PTB) rates than pregnant women without HIV (PWWH). We previously demonstrated in a cohort of PWLWH from the UK HIV Preterm Birth Network (UHPBN) study, who predominantly self-identified as having a Black ethnic background, PTB occurred in association with non-optimal CSTs III and IV. It remains unclear how these associations varied by HIV status and social factors. This larger updated analysis compares vaginal microbiota composition, inflammation, and PTB outcomes across self-identified Black and White PWLWH and PWWH. Results 135 women from the UHPBN study provided second trimester vaginal samples.  Samples were available from 55 Black PWLWH, 14 Black PWWH, 15 White PWLWH, and 19 White PWWH for these analyses. Of the 12 PTBs, 10 occurred in Black PWLWH (18% PTB rate). Black pregnant women showed the highest alpha diversity, while White PWWH had the lowest. Black women and White PWLWH exhibited a higher prevalence of CSTs III and IV and lower prevalence of CST I. Among Black women, HIV status did not influence Chao1 diversity or inflammation, whereas among White women, HIV was associated with increased Chao1 (p=0.007) and higher composite inflammation (p< 0.001). In Black PWLWH, PTB was associated with CSTs III and IV. Nearly half of Black PWLWH (49%) underwent a CST transition and were more likely to transition compared to other subgroups (Adjusted odds ratio (aOR) 0.40, 95% CI 0.15–0.98; p=0.048). Overall CST change trended toward increased PTB risk (aOR 3.50, 95% CI 0.82–18.46; p=0.10); however, transitioning between CSTs III and IV was associated with increased PTB risk (aOR 7.75, 95% CI 1.57–42.75; p=0.01). Conclusions Black PWLWH had the highest PTB rates, strongly associated with non-optimal CSTs and CST transitions during the second trimester. The high prevalence of CSTs III and IV among Black women regardless of HIV status, and among White PWLWH, may reflect broader socioeconomic determinants of reproductive health.