Anti-D administration in pregnancy for preventing rhesus alloimmunisation.

BACKGROUND

A woman may develop Rh-negative antibodies during her first pregnancy when her fetus is Rh-positive. Antibodies develop most frequently after the 28th week of gestation.

OBJECTIVES

The objective of this review was to asses the effects of giving antenatal anti-D immunoglobulin at 28 weeks or more of pregnancy on the incidence of RhD alloimmunisation when given to Rhesus negative mothers without anti-D antibodies.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register, Cochrane Controlled Trials Register, and bibliographies. Date of last search: December 1998.

SELECTION CRITERIA

Randomised trials in Rhesus negative women without anti-D antibodies given anti-D after 28 weeks of pregnancy, compared with no treatment or placebo.

DATA COLLECTION AND ANALYSIS

Data were extracted by one reviewer and double entered.

MAIN RESULTS

Two eligible trials, which involved over 4500 women, compared anti-D prophylaxis with no treatment. Although the data suggested, when women receive anti-D at 28 and 34 weeks gestation, a reduced incidence of immunisation during pregnancy (0R O.44, 95% CI 0.18-1.12), after the birth of a Rhesus positive infant (OR 0.44, 95% CI 0.18-1.12), and within 12 months after birth of a Rhesus positive infant (OR 0.44, 95% CI 0.19-1.01), none of these differences were statistically significant. In the trial, which used the larger dose of anti-D (100ug; 500IU), there was a clear reduction in the incidence of immunisation at 2-12 months following birth in women who had received Anti-D at 28 and 34 weeks (OR 0.22 95% CI 0.05-0.88). No data were available for the risk of RhD alloimmunisation in a subsequent pregnancy. No differences were observed in the incidence of neonatal jaundice.

REVIEWER'S CONCLUSIONS: The risk of RhD alloimmunisation during or immediately after a first pregnancy is about 1.5%. Administration of 100ug (500IU) anti-D at 28 weeks and 34 weeks gestation to women in their first pregnancy can reduce this risk to about 0.2% without, to date, any adverse effects. Although such a policy is unlikely to confer benefit or improve outcome in the present pregnancy, fewer women will have Rhesus D antibodies in their next pregnancy. Adoption of such a policy will need to consider the costs of prophylaxis against the costs of care for women who become sensitised and their affected infants, and local adequacy of supply of anti-D gammaglobulin.