Implications of malformations not due to amniotic bands in the amniotic band sequence.

It is widely accepted that the primary event in the amniotic band sequence (ABS) is early rupture of the amnion, and that the development of the fetus is then disrupted by entanglement and abrasion. The mechanism of the initial rupture is unknown. An argument raised in favor of this theory has been the apparent absence of non-band-derived malformations in the ABS. Here we report on four infants with ABS and additional malformations that are not readily explainable on the basis of band disruptions. These infants, together with some additional observations in the literature, and a growing number of reports of familial ABS, raise the question as to whether the formation of bands and other "non-disruption" abnormalities may have a common primary etiology in some cases. The primary mechanism could operate through disturbing the vascular system, and the factors involved might be both extrinsic or intrinsic, and some instances might date to an abnormality of the germ disk.