Buekens, Pierre (2001). Invited Commentary: Rare Side Effects of Obstetric Interventions: Are Observational Studies Good Enough?. American Journal of Epidemiology, 153(2)
In this issue of the Journal, Wen et al. (1) used an observational design to compare the side effects of vacuum extraction and forceps among babies in Quebec, Canada, who weighed between 2,500 and 4,000 g. The use of case-control and cohort designs for the general purpose of studying side effects has been recommended for more than 2 decades (2). The sample size of randomized trials is often not large enough to evaluate uncommon side effects of therapy. Observational studies of side effects of drugs are generally considered to be appropriate because the side effects often are not related to the indication for the therapy (3). For example, patients who received chloramphenicol are probably not predisposed to aplastic anemia. Another example is the development of retroperitoneal fibrosis induced by some beta-blockers (4). The retroperitoneal fibrosis is unrelated to the disease for which the beta-blockers were prescribed, and an observational study can thus provide an unbiased estimate of the risk of the side effect.
American Journal of Epidemiology