Misplaced obsession with prospectively randomized studies.

Medical care should be based on best available evidence. While randomized controlled trials (RCT) are currently considered a gold standard of study design, they are not always available and do not represent the only study format that can lead to best available evidence. This communication argues that overvaluation of RCT and undervaluation of other study formats in establishing best available evidence hurts progress in reproductive medicine and in medicine in general.