No women who took lithium during pregnancy were found among four case-control studies of Ebstein's anomaly involving 25, 34, 59, and 89 affected children, respectively. In two cohort studies, risk ratios of 3.0 (95% confidence interval [CI], 1.2 to 7.7) and 1.5 (95% CI, 0.4 to 6.8) for all congenital anomalies have been observed.