As part of a long-term follow-up of structural disorders present at birth or shortly thereafter in infants born at Group Health Cooperative of Puget Sound, all infants with a diagnosis of pyloric stenosis born between July 1, 1977 and June 30, 1982, were identified. Automated pharmacy profiles were examined to determine whether an association between maternal Bendectin use in the first trimester and infantile hypertrophic pyloric stenosis existed. Among the 3,835 women exposed to Bendectin while pregnant, in this group of 13,346 births, 13 had infants who developed pyloric stenosis, and among the 9,511 women not exposed, 13 had infants who developed pyloric stenosis, resulting in a risk ratio estimate of 2.5 (95% confidence interval (CI) 1.2-5.2). When mothers were divided according to the number of prescriptions for Bendectin filled, the relative risk estimate increased from 1.2 (95% CI 0.4-4.4) in women who filled only one prescription to 7.6 (95% CI 4.9-11.6) in women who filled five or more prescriptions for Bendectin during their pregnancy.
