• Caroline A Crowther, Philippa Middleton, and Rosemary D McBain.
• ARCH: Australian Research Centre for Health of Women and Babies, Discipline of Obstetrics and Gynaecology, The University ofAdelaide, Adelaide, Australia. caroline.crowther@adelaide.edu.au.
• Cochrane Db Syst Rev. 2013 Feb 28 (2): CD000020.

BackgroundDuring pregnancy, a Rhesus negative (Rh-negative) woman may develop antibodies when her fetus is Rhesus positive (Rh-positive). These antibodies may harm Rh-positive babies.ObjectivesTo assess the effects of antenatal anti-D immunoglobulin on the incidence of Rhesus D alloimmunisation when given to Rh-negative women without anti-D antibodies.Search MethodsWe searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 September 2012).Selection CriteriaRandomised trials in Rh-negative women without anti-D antibodies given anti-D after 28 weeks of pregnancy, compared with no treatment, placebo or a different regimen of anti-D.Data Collection And AnalysisTwo review authors independently assessed trial eligibility and risk of bias and extracted the data.Main ResultsTwo trials with moderate to high risk of bias, involving over 4500 women, compared anti-D prophylaxis with no anti-D during pregnancy. 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% confidence interval (CI) 0.15 to 1.17); after the birth of a Rh-positive infant the RR was 0.42 (95% CI 0.15 to 1.17); 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.Authors' ConclusionsThe 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% without, to date, any adverse effects. Although unlikely to confer benefit in the current pregnancy, fewer women may have Rhesus D antibodies in any subsequent pregnancy, but the effects of this needs to be tested in studies of robust design.

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