A systematic review including 9 studies (2 RCTs, 6 non-randomised CTs and 1 population-based before-and-after study) with a total of 17,398 subjects was abstracted in DARE. The OR for sensitisation with antenatal prophylaxis was 0.26 (95% CI 0.09 to 0.75) for the group that used a dosage regime of 500 IU at 28 and 34 weeks with primigravidae. The second pooling used a dosage regime of 1500 IU at 28 weeks and included both primigravidae and multigravidae participants had an OR of 0.15 (95% CI 0.09 to 0.23). The third group included all trials except those with very low doses had an OR of 0.16 (95% CI 0.11 to 0.23).