Prospective follow-up of 136 babies exposed to ecstasy in utero indicated that the drug may be associated with a significantly increased risk of congenital defects (15.4% [95% CI 8.2-25.4]). Cardiovascular anomalies (26 per 1000 livebirths [3.0-90.0]) and musculoskeletal anomalies (38 per 1000 [8.0-109.0]) were predominant.