OBJECTIVE: Despite an increase in the proportion of women who access antenatal care, mother-to-child transmission of syphilis continues to be a consequence of undiagnosed, untreated, or inadequately treated maternal syphilis. We reviewed evidence on the optimal timing of antenatal interventions to prevent mother-to-child transmission of syphilis and its associated adverse outcomes. DESIGN: Systematic review and meta-analysis of published literature. English-language articles were included if they (1) reported the gestational age at which the mother was screened or tested for syphilis; (2) reported on pregnancy outcome. No publication date limits were set. RESULTS: We identified a total of 1,199 publications, of which 84 were selected for further review and five were included. All showed a lower prevalence of any adverse outcome among women who received an intervention (to include screening and treatment) in the first and second trimesters of pregnancy compared to the third trimester. The overall odds ratio for any adverse outcome was 2.24 (95% CI 1.28, 3.93). All sub-analyses by type of outcome presented important heterogeneity between studies, except for those studies reporting an infected infant (odds ratio 2.92, 95% CI 0.66, 12.87; I(2) = 48.2%, p = 0.165). CONCLUSIONS: Our review has shown that the timing of antenatal care interventions makes a significant difference in the risk of having an adverse outcome due to syphilis. Women who sought care in the first two trimesters of their pregnancy, and received the appropriate intervention, were more likely to have a healthy infant, compared to women screened and treated in the third trimester. Encouraging ALL pregnant women to seek care in the first two trimesters of their pregnancy should be a priority for health programmes. For interventions to be effective within these health programmes, health systems and community engagement programmes need to be strengthened to enable pregnant women to seek antenatal care early.