Preparing and updating systematic reviews of randomized controlled trials of health care.

People providing health care tend to turn to review articles rather than reports of primary research when seeking information to guide their practices. For this reason, the process of reviewing the results of primary research must respect scientific principles. Reviews must be kept up to date and disseminated in appropriate ways to the people who make decisions about health care, including policy makers, practitioners, and users of the health services. This article describes the methods developed and used in an attempt to address these challenges for care during pregnancy and childbirth.