Assessing new interventions in women's health.

One of the most frequent clichés in evidence-based medicine (EBM) is that 'without evidence there can be no evidence-based practice'. How best to assemble evidence on the effectiveness (or ineffectiveness) of a treatment is central to the entire concept of EBM. Particularly in women's health, where even small or moderate improvements in the individual well-being of one woman can lead to an enormous impact on the overall health of the nation, it is important to be able to detect or refute reliably small to moderate treatment effects. Evidence must come from studies where biases and random errors have been minimised, which requires large scale randomised controlled trials, the methodology of which is relatively familiar. However, the challenges peculiar to running trials in women's health have been less fully considered. This article draws on examples from the literature to illustrate many of the principles that need to be considered when running, or assessing, a trial of an intervention in women's health.