Obstetrics & Gynecology in 1996: Marking the progress toward evidence-based medicine by classifying studies based on methodology

OBJECTIVE: To test the hypothesis that researchers in obstetrics and gynecology favor an observational type of study design. DATA SOURCES: The 12 regular issues of Obstetrics & Gynecology published during 1996 were analyzed. METHOD OF STUDY SELECTION: All articles in the journal Obstetrics & Gynecology were reviewed for the year 1996, except that separate issues covering case reports, case condensations, and reviews were excluded. TABULATION, INTEGRATION, AND RESULTS: Studies were classified as observational or experimental. Observational studies were subclassified as either descriptive, case-control, or cohort. Experimental studies were subclassified as either randomized controlled trial (RCT) or uncontrolled trial. Other study designs were noted. Of the 316 studies published during 1996, 241 (76%) were observational, 43 (14%) experimental, and 32 (10%) other. There were 162 (51%) descriptive studies, 44 (14%) case-control studies, 35 (11%) cohort studies, 35 (11%) RCTs, and eight (3%) uncontrolled trials. CONCLUSION: Researchers who publish in Obstetrics & Gynecology favor an observational study design. With evidence-based medicine growing in popularity as a new standard or paradigm, the reliance on observational studies may have implications.