BMJ  2004;329:1039-1042 (30 October), doi:10.1136/bmj.329.7473.1039

Education and debate

Inappropriate use of randomised trials to evaluate complex phenomena: case study of vaginal breech delivery

¹ Department of Obstetrics and Gynaecology, University of British Columbia, BC Women's Hospital, Vancouver, BC, V6H 3V5 Canada

As randomised trials continue to ascend in the evolution of evidence based medicine, we must recognise and respect their limitations when examining complex phenomena in heterogeneous populations

The first 150 words of the full text of this article appear below.

Introduction

Randomised controlled trials have greatly improved the quality of evidence guiding clinical practice, but when applied to complex phenomena, they have important limitations. Complex patient populations with poorly quantifiable variations between individuals present one area of difficulty; complex procedures requiring skill and clinical judgment present another. A large, well designed, and well executed randomised controlled trial of breech presentation at term, the "term breech trial," by Hannah et al rapidly dictated a new standard of care for the management of breech deliveries around the world.¹ Yet this trial failed to adequately appreciate both the complex nature of vaginal breech delivery and the complex mix of operator variables necessary for its safe conduct. Widespread acceptance of this trial's results has breached the limits of evidence based medicine.

Hannah et al's trial showed a significant increase in perinatal mortality and morbidity in women randomised to a trial of labour compared with elective . . . [Full text of this article]

Bias of licence

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A discriminating procedure

Homogenising populations and clinicians

Simplified risk reduction

Short term combined end points

The limits of evidence based medicine

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