Abstract
BACKGROUND: Adolescents in sub-Saharan Africa shoulder a disproportionate burden of sexually transmitted infections (STIs), yet data for pregnant teenagers in these settings are sparse. OBJECTIVES: The study estimated the prevalence of STI seropositivity and its associated factors, among pregnant adolescents at Mbarara Regional Referral Hospital (MRRH), Uganda. DESIGN: Hospital-based cross-sectional study. METHODS: Consecutive pregnant adolescents (10-19 years) attending the MRRH antenatal clinic or maternity ward between 1 July and 30 September 2024 were enrolled. A structured questionnaire captured socio-demographic, sexual-behavioural, obstetric, clinical and nutritional variables. Blood samples were tested for HIV (Determine™/STAT-PAK™), syphilis (Treponema pallidum haemagglutination assay) and Hepatitis B (HBsAg rapid test). The composite STI outcome was seropositivity for any infection: HIV, syphilis or HBsAg. Independent associations were examined with Firth-penalised logistic regression; adjusted odds ratios (aOR) and 95% confidence intervals (CI) are reported. RESULTS: Among 249 participants (median age 18 years, interquartile range 18-19), the overall prevalence of STI seropositivity was 12.1% (95% CI: 8.3-16.8). Prevalence by each STI was HIV 8.8%, syphilis 4.0% and HBV 0.4%. Multigravidae had higher odds of infection than primigravidae (aOR: 2.81, 95% CI: 1.01-7.84). Having ever used a non-barrier modern contraception tripled the odds of STI (aOR 3.04, 95% CI: 1.10-8.45), whereas marriage or cohabitation reduced risk by 63% (aOR 0.37, 95% CI: 0.14-0.96). CONCLUSION: Nearly one in eight pregnant adolescents at MRRH were infected with HIV, syphilis or HBV, with these STIs more likely to be among multigravidae and former users of non-barrier contraception and less likely among married/cohabiting pregnant adolescents. These findings support integrating repeat HIV-syphilis testing, dual-method contraceptive counselling and targeted interventions for multigravidae into youth-friendly antenatal services to advance STI-elimination goals.