OBJECTIVES: Malaria and curable sexually transmitted and reproductive tract infections (STIs/RTIs) are associated with adverse pregnancy outcomes. This study reports the prevalence and risk factors of curable STIs/RTIs, STI/RTI co-infection and STI/RTI and malaria co-infection among HIV-negative pregnant women at their first antenatal care visit in Kenya, Malawi and Tanzania. METHODS: HIV-negative pregnant women of all gravidae (n=4680) were screened for syphilis with point-of-care tests and treated if positive. Separately, women provided blood samples (n=4569) for rapid plasma reagin (RPR) testing; positive cases were confirmation by Treponema pallidum particle agglutination (TPPA). Women also provided dried blood spots for batch testing of malaria by retrospective polymerase chain reaction (PCR (n=4226) methods. A randomly selected subgroup of women provided vaginal swabs for chlamydia, gonorrhoea and trichomoniasis testing by retrospective PCR batch testing (n=1431), and bacterial vaginosis diagnosis by Nugent scoring (n=1402). RESULTS: Malaria prevalence was 14.6% (95% CI 13.6 to 15.7), 45.9% (43.4 to 48.4) of women were positive for at least one curable STI/RTI and 6.7% (5.5 to 8.1) were co-infected with malaria and a curable STI/RTI. Prevalence of individual STIs/RTIs ranged from 28.5% (26.2 to 30.9) for bacterial vaginosis to 14.5% (12.7 to 16.4) for trichomoniasis, 13.8% (12.1 to 15.7) for chlamydia, 2.7% (1.9 to 3.6) for gonorrhoea and 1.7% (1.4 to 2.2) for RPR/TPPA-confirmed syphilis. The prevalence of STI/RTI co-infection was 10.1% (8.7 to 11.8). Paucigravidae, at highest risk of malaria, were also at greater risk of having chlamydia, gonorrhoea and bacterial vaginosis than multigravidae. CONCLUSIONS: Of women infected with malaria, 49.0% also had a curable STI/RTI and one in five women with at least one STI/RTI were co-infected with more than one STI/RTI. Current antenatal interventions that address malaria and curable STIs/RTIs remain suboptimal. New approaches to preventing and managing these infections in pregnancy are urgently needed. TRIAL REGISTRATION NUMBER: NCT03208179.