Two major patterns of nongenetic malformations are found at autopsy

Patterns of malformations seen in autopsies may contribute to the understanding of their pathogenetic mechanisms. Two entities, acardiac twins (ATs) and amniotic band disruption complex (ABDC), have distinct patterns, indicating different mechanisms, namely vascular perfusion deficit and external disruption. With ATs and ABDC as model groups, this study was undertaken to see if other dysmorphic infants with the characteristic defects of these models formed distinct and numerically important groups. A total of 192 autopsies with nongenetic malformations was divided into groups including (1) those with defects found in the ATs but not in the ABDC, (2) those with defects found only in the ABDC, and (3) those with a mixture of exclusive defects from each model group. The cases followed the characteristic defects of ATs or ABDC in 20% (group 1) and 28% (group 2), respectively, forming 2 large and distinct groups; only 4% had mixed malformations (group 3). Group 1 had different characteristics from group 2 as a result of the frequent multiple malformations, often with congenital heart defects (CHDs), internal and inferior malformations. These cases were probably related to a vascular perfusion deficit. Group 2 had a majority of females and single, external, and superior defects, but it lacked CHDs and inferior malformations. These cases were likely due to external disruption. Two large and distinct groups of autopsies with nongenetic malformations were thus identified, and their mechanisms are proposed to be similar to those of the model groups.