Comment: The quality of evidence is downgraded by study quality (unclear allocation concealment, lack of blinding, incomplete outcome data).
A Cochrane review included 2 studies with a total of 4 500 subjects comparing anti-D prophylaxis with no anti-D during pregnancy. The risk of Rhesus D alloimmunisation during or immediately after a first pregnancy is about 1%. When women received anti-D at 28 and 34 weeks' gestation, risks of immunisation were not significantly different than for women not given antenatal anti-D: risk ratio (RR) of immunisation during pregnancy was 0.42 (95% CI 0.15 to 1.17; 2 trials, n=3 852); after the birth of a Rh-positive infant the RR was 0.42 (95% CI 0.15 to 1.17; 2 trials, n=2 297); and within 12 months after birth of a Rh-positive infant the RR was 0.39 (95% CI 0.10 to 1.62). However, women receiving anti-D during pregnancy were significantly less likely to register a positive Kleihauer test (which detects fetal cells in maternal blood) in pregnancy (RR 0.60, 95% CI 0.41 to 0.88) and at the birth of a Rh-positive infant (RR 0.60, 95% CI 0.46 to 0.79). No data were available for the risk of Rhesus D alloimmunisation in a subsequent pregnancy. No significant differences were seen for neonatal jaundice, and no adverse effects were reported in either trial. The number needed to treat was 213 women.
Comment:The risk of Rhesus D alloimmunisation during or immediately after a first pregnancy is about 1%. Administration of 100 µg (500 IU) anti-D to women in their first pregnancy can reduce this risk to about 0.2%
NoteDate of latest search: 14 November 2012