HIV and Syphilis in Pregnancy: A Cross-Sectional Analysis from Healthcare Facilities in Southern Tanzania

Syphilis, caused by Treponema pallidum , is a chronic infection transmitted sexually, through blood transfusion, or vertically from mother to fetus. In pregnancy, it poses a significant public health risk, particularly in developing countries like Tanzania, contributing to perinatal morbidity and mortality. However, data on syphilis and its risk factors, especially among pregnant women living with HIV, are scarce. This study aimed to assess the burden and identify risk factors for syphilis infection among HIV-infected pregnant women attending Prevention of Mother-to-Child Transmission clinic services in selected health facilities in the Mtwara region. This health facility-based cross-sectional study was conducted over three months among pregnant women living with HIV attending Prevention of Mother-to-Child Transmission clinic services in the Mtwara region. A structured questionnaire was used to gather demographic, clinical, and laboratory data. Blood samples (4 ml) were collected for syphilis screening and confirmatory tests. Bivariate and multivariate logistic regression analyses identified significant factors associated with syphilis infection in pregnant women, with a p -value <0.05 considered significant. Two hundred and twenty (n=220) pregnant women living with HIV were enrolled in this study. The median age of the participants was 32.7 years (IQR: 27.6-37.6). The majority (45.5%) of the participants were married, 71.4% had primary education, 47.7% were unemployed, 77.7% were multigravida, and 40.5% were in the second trimester. The prevalence of syphilis infection was 10.9% (24/220). In addition, being in the second trimester of the gestation period [aOR=5.69: 95% CI 1.44-22.46, p =0.013] and being infected with hepatitis B virus [aOR=31.39: 95% CI 9.45-104.23, p <0.001] were independent factors associated with syphilis infection among pregnant women living with HIV in the Mtwara region. The study revealed a significant burden of syphilis infection among pregnant women living with HIV in the Mtwara region, with advanced gestational age (especially in the second trimester) and co-infection with hepatitis B virus identified as key risk factors. The findings emphasize the importance of routine, integrated screening for syphilis and other infections, including hepatitis B, to reduce infection burden, prevent vertical transmission, and improve maternal and child health outcomes.