HIV and syphilis coinfection in pregnancy and adverse birth outcomes in Uganda

Background Despite increasing syphilis incidence worldwide, little is known about the combined impact of maternal HIV and syphilis coinfection. We determined effects of HIV/syphilis coinfection in pregnancy on birth outcomes. Methods We conducted two prospective birth cohort studies of pregnant women delivering in Uganda from 2017-2023. Our primary outcome was birthweight. Our secondary outcome was a composite adverse birth outcome, including low birthweight (<2.5kg), stillbirth, early neonatal death, or 5-minute APGAR<7. We compared outcomes by HIV and Treponema pallidum particle agglutination assay (TPPA) seropositivity and fitted multivariable logistic regression models to determine associations with outcomes. Results Overall, TPPA seroprevalence was 12% (118/967) in this cohort comprised of 50% women with HIV (WHIV); 19% (94/483) among WHIV and 5% (24/484) among women without HIV. Only 48% of TPPA seropositive women reported syphilis testing during antenatal care. Combined stillbirth and early neonatal death were higher among TPPA seropositive participants: 12% (15/118) vs 4% (32/849) among seronegatives. Low birthweight was associated with HIV seropositivity (-0.1kg, 95%CI -0.15, -0.04), younger maternal age (0.01kg per year increase, 95% CI 0.01,0.02), and lower gestational age (0.07kg per week increase, 95% CI 0.06,0.09), but not TPPA serostatus. The composite adverse birth outcome was associated with lower maternal and gestational age at birth. Conclusion We report high TPPA seroprevalence, low syphilis testing rates in antenatal care, and significant associations with adverse birth outcomes among WHIV in Uganda, emphasizing the need to improve prenatal syphilis testing and treatment.