Can the Pill Cause Birth Defects?

The difficulties in documenting causal relations between environmental agents and birth defects are well recognized. Epidemiologic surveys and surveillance studies should, in theory, be productive approaches to identifying environmental teratogens. In practice, however, a gradual accumulation of clinical reports by alert practitioners, followed by retrospective studies of cohorts assumed to be at risk (and infrequently by prospective studies), has proved more successful. Because there may be multiple causes for similar defects, the definition of a specific cause is greatly assisted if there are clusters of cases, unusual or characteristic anomalies, or other unique features to attract the attention of the . . .