Intended for healthcare professionals

Clinical Review Fortnightly review

Drug treatment during pregnancy

BMJ 1998; 317 doi: (Published 28 November 1998) Cite this as: BMJ 1998;317:1503
  1. Peter Rubin, dean
  1. Dean's Office, Faculty of Medicine and Health Sciences, Medical School, Queen's Medical Centre, Nottingham NG7 2UH

    For most doctors prescribing a drug to a pregnant woman is like taking a journey through uncharted territory; navigation is made no easier by the darkness cast by “thalidomide's long shadow.”1 The usual benchmarks are absent because evidence from large clinical trials doesn't exist for drug treatment during pregnancy. Information on many drugs includes non-specific warnings along the lines of “not to be used in pregnancy unless the benefits outweigh the risks,” even though the benefits may not have been confirmed and the risks are not specified. Also, the disease being treated may affect or be affected by pregnancy. Nevertheless, at least a third of all pregnant women in the United Kingdom are prescribed at least one course of drug treatment.2 The purpose of this review is to summarise some of the important points that should be considered when prescribing drugs for pregnant women.

    Summary points

    • Evidence about the effects and effectiveness of drug treatment during pregnancy is often circumstantial

    • All doctors who prescribe drugs for women of childbearing age must think about potential pregnancies before prescribing

    • Counselling before pregnancy is essential for all women receiving long term drug treatment

    • A useful treatment should not be stopped without good reason


    For obvious ethical reasons there are few randomised and placebo controlled clinical trials designed to evaluate the safety and efficacy of drugs in pregnancy. Exceptions to this rule include studies of aspirin in the prevention of pre-eclampsia 3 4 and some small studies of antihypertensive agents. 5 6 Studies of drug treatment during pregnancy are usually done as retrospective analyses (performed by reviewing charts or monitoring prescriptions) or case reports. Case reports are important in recording alleged adverse effects but suffer from the weakness of being anecdotal evidence. The problem is that in 1-2% of all pregnancies in developed countries …

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