The generalizability of trial data; a comparison of beta-blocker trial participants with a prospective cohort of women taking beta-blockers in pregnancy

Objective: To evaluate the generalizability of randomized controlled trial (RCT) data to obstetric practice. using the example of beta -blocker therap y. Study design: Descriptive comparison of characteristics of participants, interventions, and outcomes assessed between a meta-analysis of trials of beta -blocker therapy in pregnancy. and a prospective cohort of beta -block er exposed callers to Motherisk, a Teratology Information Service. Results: 72 women (cohort) and 34 trials with 2474 participants (meta-analysis) wer e compared. The generalizability of trials was limited by an inadequate des cription of maternal demographics and indications for beta -blockers, and a focus on the effectiveness of beta -blockers as antihypertensives rather t han on reproductive risks. Conclusions: Some of these limitations could he rectified. Others cannot, such as evaluation of teratogenicity (for ethical reasons) or all indications for a drug (for practical reasons). Reference to observational literature is, and will likely remain, necessary to addres s the 'harm' side of the therapeutic equation in pregnancy. (C) 2001 Elsevi er Science Ireland Ltd. All rights reserved.