Anti-D administration in pregnancy for preventing Rhesus alloimmunisation

Crowther CA, Middleton P

Published Online:

January 21, 2009

Anti-D given during pregnancy at 28 and 34 weeks of pregnancy reduces incidence of antibody formation and probably also reduces immunisation of women.

Women whose blood group is Rh-negative sometimes form Rh-antibodies when carrying a Rh-positive baby. This is more likely during birth, but occasionally happens in late pregnancy. It can cause anaemia, and sometimes death, for a Rh-positive baby in a subsequent pregnancy. Giving the mother anti-D after the first birth does reduce the problems, but giving anti-D during pregnancy is likely to help as well, although more research is required to confirm these possible benefits and identify possible harms.

Abstract (click to read)

Background:

During pregnancy, a Rhesus negative (Rh-negative) woman may develop antibodies when her fetus is Rhesus positive (Rh-positive). These may harm Rh-positive babies.

Objectives:

To 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 strategy:

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (June 2007), and bibliographies.

Selection criteria:

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

Data collection and analysis:

One review author extracted and double-entered data; these were checked by another review author.

Main results:

Two average to poor-quality trials, involving over 4500 women, compared anti-D prophylaxis with no treatment. When women received anti-D at 28 and 34 weeks' gestation, relative risk (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 0.41 (95% CI 0.16 to 1.04). While none of these differences were statistically significant, the risk difference (RD) between anti-D and no treatment was significant (RD -0.01, 95% CI -0.01 to 0.00) suggesting reduced incidence of immunisation after anti-D prophylaxis.

In the higher dose trial (100 µg; 500 international units (IU) anti-D), there was a nonsignificant reduction in immunisation at two to 12 months following birth of a Rh-positive infant in women who had received anti-D (RR 0.14, 95% CI 0.02 to 1.15). However, women receiving anti-D 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 differences were seen for neonatal jaundice.

Authors' conclusions:

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% 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.

This record should be cited as:

Crowther CA, Middleton P. Anti-D administration in pregnancy for preventing Rhesus alloimmunisation. Cochrane Database of Systematic Reviews 1999, Issue 2. Art. No.: CD000020. DOI: 10.1002/14651858.CD000020

Assessed as up to date:

June 26, 2007

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Primary Review Group:

Pregnancy and Childbirth Group

Health topics:

Pregnancy & childbirth > Blood group incompatibilities

Cochrane Summaries^beta

Independent high-quality evidence for health care decision making

Anti-D administration in pregnancy for preventing Rhesus alloimmunisation

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