Randomized trials versus observational studies in adolescent pregnancy prevention

The objective of this study is to compare the results of randomized trials and observational studies of interventions to prevent adolescent pregnancy. We identified published and unpublished reports through computerized searc hes of CATLINE, CINAHL, CONFERENCE PAPERS INDEX, DISSERTATION ABSTRACTS ONL INE, EMBASE, ERIC, MEDLINE, NTIS, POPLINE, PsycINFO, and SOCIOLOGICAL ABSTR ACTS; manual searches of eight relevant journals; reference lists from prim ary articles; and contact with content experts. We included randomized tria ls and observational studies that evaluated the impact of primary preventio n interventions including sex education classes, school-based clinics, free -standing clinics, physician/nurse practitioner practice-based service, imp roved access, and community-based programs on four outcomes: sexual interco urse, birth control use, responsible sexual behavior, or pregnancy in adole scents. One investigator abstracted the data and a second conducted a detai led review of the abstraction. We identified 13 randomized trials and 17 ob servational studies. We generated estimates of the impact of the interventi ons separately for males and females for all four outcomes for both observa tional studies and randomized trials. For six of the eight outcomes the sum mary odds ratios for the observational studies showed a significant interve ntion benefit (P < 0.05) while the randomized trials did not show a benefit for any outcome in either females or males. The difference between the res ults of the observational studies and randomized trials was statistically s ignificant in two of the eight outcomes (P < 0.05 for initiation of interco urse and pregnancy in females). Observational studies yield systematically greater estimates of treatment effects than randomized trials of adolescent pregnancy prevention interventions. Public policy or individual patient tr eatment decisions should be based on observational studies only when random ized trials are unavailable and only with careful consideration of possible biases. (C) 2000 Elsevier Science Inc. All rights reserved.