Comparison of the amniotic band disruption complex with acardiac twins does not support its vascular origin

The amniotic band disruption complex (ABDC) has been attributed to vascular disruption by some authors, not by others. Acardiac twins (ATs), however, have been generally accepted as a prime example of vascular disruption. In this study a comparison was made of these two entities to determine if they were similar or not, and thus we attempted to resolve the controversy of the mechanisms in the ABDC. A female tendency (2:1) was found in the ABDC in contrast to the "normal" sex distribution (0.88:1) in the ATs (p < 0.001). Most types of malformations (66%) were mutually exclusive, notably those of the cranium/brain, abdominal wall, and most internal organs; 83% were more significantly related to one or other of the entities. The ABDC malformations tended to occur unilaterally, but in the ATs they occurred bilaterally (p < 0.0001); the former tended to involve external organs and the latter internal organs (p < 0.0001). With so many differences, the two entities are unlikely due to the same mechanism: the ABDC is more likely to be due to external disruption.