Constrictive amniotic bands, amniotic adhesions, and limb-body wall complex: discrete disruption sequences with pathogenetic overlap.

In a fetopathologic evaluation of 18 cases with amniotic bands, we discerned 3 types of lesions: (1) constrictive tissue bands, (2) amniotic adhesions, and (3) more complex anomaly patterns, designated as limb-body wall complex (LBWC). Constrictive bands are caused by primary amnion rupture with subsequent entanglement of fetal parts (mostly limbs) by shriveled amniotic strands. Adhesive bands are the result of a broad fusion between disrupted fetal parts (mostly cephalic) and an intact amniotic membrane. Most of the craniofacial defects (encephaloceles and/or facial clefts) occurring in these fetuses are not caused by constrictive amniotic bands, but are the result of a vascular disruption sequence with or without cephalo-amniotic adhesion. Our observations confirm the fact that amnion rupture is not a conditio sine qua non for the development of LBWC. However, LBWC is often complicated by rupture of the unsupported amnion with ensuing formation of constrictive bands. We think that the concept that considers the 3 lesions in question as a single pathogenetic entity is erroneous and will inevitably lead to a never-ending debate between followers of the 2 prevailing theories. In our view, the theories of Streeter and Torpin are not mutually exclusive but rather apply to different types of lesions. The recognition of constrictive amniotic bands, amniotic adhesions, and LBWC as discrete but often combined disruption sequences with important pathogenetic overlap may resolve many dilemmas in interpretation when a fetus exhibits classical constrictive bands beside more severe defects.