Authors' objectives:

The overall aim of the report was to evaluate the clinical effectiveness of antenatal anti-D prophylaxis (AADP) for pregnant women who are rhesus D (RhD)-negative, and the comparative cost-effectiveness of:

- offering routine AADP to all pregnant women who are RhD-negative - offering routine AADP only to primigravidae who are RhD-negative - not offering routine AADP.

In each case, it was assumed that the current programme of offering anti-D antenatally to all RhD-negative women who suffer a potential sensitising event, and post-partum to all RhD-negative women delivered of a RhD-positive infant, will continue.

Authors' results and conclusions: In all studies, the proportion of women sensitised was lower in the intervention arm than in the control arm, although in some studies the difference was small and not statistically significant. Two doses of anti-D at 28 and 34 weeks gestation appeared to be more effective than one dose at 34 weeks only. There appeared to be no significant difference between the effectiveness of two doses of 500 IU and two doses of 1500 IU. Although there was no evidence relating to the relative effectiveness of two doses of 1250 IU, it is unlikely that this will differ significantly from that of two doses of 1500 IU. The best indication of the likely efficacy of a programme of routine AADP in England and Wales came from two non-randomised community-based studies. The pooled results of these studies suggested that such a programme may reduce the sensitisation rate from 0.95% to 0.35%. This gave an odds ratio for the risk of sensitisation of 0.37, and an absolute reduction in risk of sensitisation in RhD-negative mothers carrying a RhD-positive child of 0.6%. Although the number of such women needed to treat (NNT) to avoid one case of sensitisation was 166 (1/0.006), antenatally a RhD-negative woman will not know if she is carrying a RhD-positive child. Thus all RhD-negative pregnant women would require treatment, and not just the 60% who are carrying a RhD-positive child, making the overall NNT 278 (10/6 x 166). It was estimated that currently 625 sensitisations of RhD-negative women per year lead to a total of at least 30 fetal deaths, stillbirths, neonatal and postneonatal deaths. Avoidance of sensitisation can thus be expected to avoid fetal/neonatal loss in 4.8% of cases. The NNT to avoid a fetal or neonatal loss in a subsequent pregnancy can therefore be estimated as approximately 5790.

Authors' recommendations: The evidence suggests that routine AADP is effective in reducing the number of RhD-negative pregnant women who are sensitised during pregnancy. However, it cannot prevent all instances of sensitisation, some of which occur either despite or before appropriate administration of anti-D. Some cases of sensitisation in the UK are due to failure to adhere to the existing guidelines for the administration of anti-D either post-partum or in response to potential sensitising events. It should therefore be possible to reduce sensitisation rate by stricter adherence to current guidelines, and it could be argued that this should be pursued before initiating guidelines for the routine offering of AADP to pregnant women who are RhD-negative.

Authors' methods: Systematic review

Project Status: Completed

URL for project: http://www.hta.ac.uk/1244

Year Published: 2003

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: England, United Kingdom

Organisation Name: NIHR Health Technology Assessment programme

Contact Address: NIHR Journals Library, National Institute for Health and Care Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK

Contact Name: journals.library@nihr.ac.uk

Contact Email: journals.library@nihr.ac.uk

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