Multicentre randomised controlled trials in obstetrics and gynaecology: an analysis of trends over three decades.

To assess the trend in multicentre randomised controlled trials (RCTs), a database of 670 RCTs was assembled from four generic obstetric and gynaecological journals (Acta Obstetricia et Gynecologica Scandinavica, British Journal of Obstetrics & Gynaecology, Obstetrics & Gynecology and American Journal of Obstetrics & Gynecology) for 1975, 1980, 1985, 1990, 1995, 2000 and 2005. During this period, there was an inflationary trend with the proportion of published multicentre RCTs (from 12.9% in 1975 of all RCTs to 23.8% in 2005; P = 0.008). Multicentre RCTs had multiauthored publications (OR = 2.90; 95% CI 1.99-4.22) and more often received external funding (OR = 2.41; 95% CI 1.70-3.48) than single centre RCTs. The inflationary trend in multicentre RCTs requiring funding and collaboration represents the increasing complexity of medical research necessary to underpin evidence-based practice.