Participation in clinical trials improves outcomes in women's health: a systematic review and meta-analysis.

<bold>Background: </bold>Previous reviews examining the effect of participation in trials on outcomes have not consistently shown benefit. Obstetrics and gynaecology is a unique disease area posing challenges for both researchers and patients.<bold>Objectives: </bold>To determine whether participation in randomised controlled trials (RCTs), compared with non-participation, has a beneficial effect on women's health.<bold>Search Strategy: </bold>Medline, Embase, the Cochrane Library, and PsycInfo were searched up to December 2015.<bold>Selection Criteria: </bold>We selected studies that reported the same clinical outcomes for participants in a women's health RCT and a comparable non-participant cohort.<bold>Data Collection and Analysis: </bold>Data were extracted on quality, characteristics and study results. Outcomes were compared using logistic regression.<bold>Main Results: </bold>There were 21 relevant studies (20 160 women, 4759 outcome events). Trial participants, compared with non-participants, had 25% better odds of improved outcomes on average (OR 0.75; 95% CI 0.64-0.87; I2  = 64.3%). The beneficial effect of participating in a trial was larger in comparisons where: RCTs were of high quality (OR 0.62; 95% CI 0.50-0.76) versus low (OR 0.92; 95% CI 0.74-1.16); and RCT intervention was not available to non-participants (OR 0.57; 95% CI 0.47-0.69) versus when it was (OR 1.13; 95% CI 0.89-1.44). The effect of trial participation was not influenced by effect size within the RCT (P = 0.48), whether funding was received or not (P = 0.13), whether non-participants received any treatment or not (P = 0.49), and the quality of the comparison of RCT participants with non-participants (P = 0.88).<bold>Conclusions: </bold>Women participating in RCTs on average experienced better outcomes compared with those outside trials.<bold>Tweetable Abstract: </bold>Participants in obstetric and gynaecology RCTs experience better outcomes compared with non-participants. [ABSTRACT FROM AUTHOR]