Prevalence of sexually transmitted infection in pregnancy and their association with adverse birth outcomes: a case-control study at Queen Elizabeth Central Hospital, Blantyre, Malawi

Background There are limited data on the epidemiology of sexually transmitted infections (STI) and their contribution to adverse birth outcomes (ABO) in sub-Saharan Africa (SSA). We performed a case-control study to assess the prevalence of STI and their association with ABO among women attending Queen Elizabeth Central Hospital, Blantyre, Malawi.Methods A composite case definition for ABO included stillborn, preterm and low birthweight infants and infants admitted to neonatal intensive care unit within 24 hours of birth. Following recruitment of an infant with an ABO, the next born healthy infant was recruited as a control. Multiplex PCR for Neisseria gonorrhoeae (NG), Chlamydia trachomatis (CT) and Trichomonas vaginalis (TV) was performed on maternal vaginal swabs. HIV and syphilis status was determined on maternal and infant serum. For syphilis, we used combined treponemal/non-treponemal rapid point-of-care tests in parallel with rapid plasma reagin tests, PCR for Treponema pallidum and clinical parameters to diagnose and stage the infection. We compared STI positivity between cases and controls.Results We included 259 cases and 251 controls. Maternal prevalence of STI was 3.1%, 2.7% and 17.1% for NG, CT and TV, respectively. Maternal prevalence of untreated syphilis was 2.0% and 6.1% for early stage and late/unknown stage, respectively; prevalence of treated syphilis was 2.7%. The HIV prevalence was 16.5%. HIV infection significantly increased the odds for ABO (OR=3.31; 95% CI 1.10 to 9.91) as did NG positivity (OR=4.30; 95% CI 1.16 to 15.99). We observed higher rates of ABO among women with untreated maternal syphilis (early: OR=7.13; 95% CI 0.87 to 58.39, late/unknown stage: OR=1.43; 95% CI 0.65 to 3.15). Maternal TV and CT infections were not associated with ABO.Conclusion STI prevalence among pregnant women in Malawi is comparable to other SSA countries. HIV, NG and untreated syphilis prevalence was higher among women with ABO compared with women with healthy infants.