COLLECTING THE EVIDENCE SYSTEMATICALLY - ENSURING THAT IT IS COMPLETEAND UP-TO-DATE

A complete and comprehensive search of the relevant evidence is an ess ential step in the preparation of a scientific systematic review. The Cochrane Pregnancy and Childbirth Database consists of some 600 system atic reviews, based on almost 6,000 randomized or quasi-randomized tri als of care during pregnancy and childbirth. As ascertainment from ele ctronic search of the National Library of Medicine MEDLINE database wa s not complete, the mainstay of our search strategy was a systematic h and search of some 60 journals, beginning with volumes published in 19 50. Additional references were obtained from the list of references in primary research reports and conference reports. A major effort was m ade to identify unpublished trials and to obtain unpublished data from published trials.