Ebstein's malformation of the tricuspid valve: genetic and environmental factors. The Baltimore-Washington Infant Study Group.

Ebstein's anomaly is a specific structural deformity of the tricuspid valve, and its rarity has hampered etiologic evaluation. Cases of Ebstein's anomaly registered in the Baltimore Washington Infant Study (BWIS), a regional case-control study of cardiovascular malformations (CVM) in infancy, are reviewed. Between 1981 and 1989 a total of 4,390 CVM cases, including 47 Ebstein cases, and 3,572 controls were registered. The prevalence of Ebstein's anomaly was 5.2 per 100,000 livebirths. Additional cardiac anomalies were present in 38.3% of Ebstein cases. Non-cardiac malformations were present in 19.1% of Ebstein cases vs. 25.5% of other CVM, and 1.7% of controls. Case-fatality by 1 year of age was 23.4% in Ebstein vs. 18.1% in other CVM. Interviews of parents of Ebstein cases, other CVM, and controls (n = 44, 3,335, and 3,572, respectively) elicited information on family history of malformations, maternal illnesses, reproductive history, therapeutic drugs, parental lifestyle, and environmental exposures during the periconceptional period. Case-control analyses suggest genetic, reproductive, and environmental risk factors: twins [odds ratio (OR) 8.2, 95% confidence interval (CI) 2.6-25.3]; family history of CVM (OR 6.4, 95% CI 1.8-22.2); white race (OR 2.9 with non-whites as reference, 95% CI 1.2-7.0); previous miscarriages (OR 2.0, 95% CI 1.2-3.3); maternal exposure to benzodiazepines (OR 5.4, 95% CI 1.5-19.1); and varnishing (OR 3.4, 95% CI 1.3-9.1). Additional multicenter investigations are warranted to elucidate the role of genetic, reproductive, and environmental factors in the etiology of this anomaly.