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Anti-D administration in pregnancy for preventing Rhesus alloimmunisation

  • Review
  • Intervention

Authors

  • Caroline A Crowther,

    Corresponding author
    1. The University of Adelaide, ARCH: Australian Research Centre for Health of Women and Babies, Discipline of Obstetrics and Gynaecology, Adelaide, South Australia, Australia
    • Caroline A Crowther, ARCH: Australian Research Centre for Health of Women and Babies, Discipline of Obstetrics and Gynaecology, The University of Adelaide, Women's and Children's Hospital, 72 King William Road, Adelaide, South Australia, 5006, Australia. caroline.crowther@adelaide.edu.au.

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  • Philippa Middleton

    1. The University of Adelaide, ARCH: Australian Research Centre for Health of Women and Babies, Discipline of Obstetrics and Gynaecology, Adelaide, South Australia, Australia
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Abstract

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 methods

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.

Plain language summary

Anti-D administration in pregnancy for preventing Rhesus alloimmunisation

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.

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