Characterization of Vaginal Microbiome and Its Association with Preterm Birth Risk in HIV-Positive Pregnant Women in Rivers State

The vaginal microbiome composition is increasingly recognized as a determinant of preterm birth risk, and HIV infection may further alter microbial ecology in ways that amplify this risk in pregnant women. This prospective cohort study characterized the vaginal microbiome and assessed its relationship to preterm birth outcomes in HIV-positive versus HIV-negative pregnant women attending antenatal care at the University of Port Harcourt Teaching Hospital, Rivers State, in the South South geopolitical zone of Nigeria. Vaginal swab samples from 80 HIV-positive and 80 HIV-negative pregnant women enrolled at 16 to 20 weeks of gestation were processed for 16S rRNA gene amplicon sequencing on an Illumina MiSeq platform targeting the V4 region. Obstetric outcomes were tracked until delivery. HIV-positive pregnant women demonstrated significantly lower Lactobacillus dominance and greater microbial diversity compared to HIV-negative controls. Lactobacillus crispatus was dominant in only 21.3 percent of HIV-positive women versus 51.3 percent of HIV-negative women. Gardnerella vaginalis and Sneathia amnionii were disproportionately enriched in HIV-positive women. Preterm birth rate was 17.5 percent in HIV-positive women versus 7.5 percent in HIV-negative women. Lactobacillus-depleted community state types were independently associated with preterm birth after adjusting for antiretroviral therapy and CD4 count. These findings highlight vaginal dysbiosis as a modifiable risk factor for preterm birth in HIV-positive women and advocate for vaginal microbiome assessment in antenatal HIV care. Keywords: vaginal microbiome, HIV, preterm birth, Rivers State, Lactobacillus.