Atrioventricular septal defects: Possible etiologic differences between complete and partial defects

Background Recent advances in clinical, pathological, and genetic aspects of atrioventricular septal defects (AVSD) have set the stage for epidemiologic investigations into possible risk factors. Previous analyses of the total case group of AVSD included complete and partial subtypes without analysis of the subsets. Methods To address the question of possible morphogenetic heterogeneity of AVSD, the Baltimore–Washington Infant Study data on live‐born cases and controls (1981–1989) was reanalyzed for potential environmental and genetic risk‐factor associations in complete AVSD (n = 213), with separate comparisons to the atrial (n = 75) and the ventricular (n = 32) forms of partial AVSD. Results Complete and ventricular forms of AVSD had a similar proportion of isolated cases (12.2% and 15.6%, respectively, without associated extracardiac anomalies) and high rates of Down syndrome, whereas the atrial form of partial AVSD included 55% isolated cases. Trisomy 18 occurred in 22% of infants with the ventricular form, compared with