Routine infectious diseases screening of Sudanese pregnant women has been patchy due to scarcity of healthcare resources and social stigma. We sought to determine the seroprevalence of HIV, hepatitis B, and syphilis among pregnant women attending antenatal care (ANC) at El Obeid Maternity Hospital in western Sudan. We also explored the association between these infections and a set of socio-demographic and maternal variables. Unlinked anonymous testing for HIV-1/2 antibodies, hepatitis B surface antigen, and Treponema pallidum antibodies was performed on residual blood samples collected during routine ANC (August 2016-March 2017). Seroprevalence of HIV was 1.13% (5/444; 95% CI 0.37-2.61%), hepatitis B 2.93% (13/444; 95% CI 1.57-4.95%), and syphilis 7.43% (33/444; 95% CI 5.17-10.28%). On bivariate analysis, there were no statistically significant associations between hepatitis B, syphilis, or a composite outcome including any of the three infections and age, stage of pregnancy, gravidity, parity, previous mode of delivery, history of blood transfusion, or husband polygamy. Urgent action is needed to scale up routine maternal screening for HIV, hepatitis B, and syphilis on an opt-out basis. Further research into the socio-demographic and behavioural determinants of these infections as well as their clinical outcomes is needed.