British National Formulary Guidance on prescribing in pregnancy: A descriptive cross-sectional study

To assess how well pregnancy-specific guidance within the British National Formulary supports healthcare professionals to facilitate safe and effective medication use.

We performed a manifest content analysis of the text of all pregnancy sections within British National Formulary drug monographs, with inductive and iterative coding. We included all 1752 medications listed within the British National Formulary on 11 February 2025. No medications were excluded. Medications were categorized into combinations, specialist, monoclonal antibody or fragment crystallizable domain fusion proteins; and black triangle medications. We developed codes that classified the guidance provided, reasons for provided guidance and sources of guidance.

A pregnancy section was available for 1138 (65%) of medications listed within the British National Formulary. Information provided was heterogenous, with over 547 unique text statements. Of medications with a pregnancy section, only 41 (3.6%) were coded as 'use without restriction' and 186 (16%) did not provide clear guidance on whether the medication could be used in pregnancy. Reasons for provided guidance were primarily due to known toxicity in humans or animals (45%) or a lack of information on the medication's effect in pregnancy (24%). The source of guidance was primarily not stated (56%) or the manufacturer (40%).

Information on prescribing in pregnancy within the British National Formulary does not facilitate safe and effective use of medicines in pregnancy. Improvements could include signposting to resources with more detailed information and by standardizing guidance statements. More widely, there is a need for better prescribing information in pregnancy.