ObjectiveMycoplasma genitalium (MG) is a sexually transmitted organism associated with cervicitis and pelvic inflammatory disease in women and has been shown to increase the risk of HIV acquisition and transmission. Little is known about the prevalence and incidence of MG in pregnant women. Our study sought to evaluate the prevalence and incidence of MG infection in HIV-infected and HIV-uninfected pregnant women.MethodsWe conducted a cohort study of 197 women ≥18 years receiving antenatal care in South Africa from November 2017 to February 2019. We over-recruited HIV-infected pregnant women to compare MG by HIV infection status. Self-collected vaginal swabs, performed at the first antenatal visit, third trimester and within 1 week post partum, were tested for MG using the Aptima assay (Hologic, USA). We report on the prevalence and incidence of MG and used multivariable logistic regression to describe correlates of MG and adverse pregnancy and birth outcomes (preterm delivery, miscarriage and vertical HIV transmission), adjusting for maternal age and HIV infection status.ResultsAt first antenatal visit, the median age was 29 years (IQR=24–34) and the gestational age was 19 weeks (IQR=14–23); 47% of women enrolled in the study were HIV-infected. MG prevalence was 24% (95% CI 16% to 34%, n=22) in HIV-infected and 12% (95% CI 6.8% to 20%, n=13) in HIV-uninfected pregnant women. MG incidence during pregnancy and early post partum was 4.7 infections per 100 woman-years (95% CI 1.2 to 12.9) or 3.9 per 1000 woman-months (95% CI 1.0 to 10.7). Adjusting for maternal age, HIV-infected women had over three times the odds of being infected with MG (adjusted OR=3.09, 95% CI 1.36 to 7.06).ConclusionWe found a high prevalence and incidence of MG in pregnant women. Younger maternal age and HIV infection were associated with MG infection in pregnancy. Further research into birth outcomes of women infected with MG, including vertical transmission of HIV infection, is needed.