The authors present a critical revision of the literature concerning the pathogenic hypotheses and the opinions, during the centuries, about the origin of the deformities caused by amniotic bands. Here they describe two cases of severe deformities caused by amniotic bands which can be classified in types I and V according to Onnipoff and Hall. In the first case the newborn died immediately after the birth: the other one lives in good health after multiple surgical operations. In accordance with the anatomical reports that were found using very specific techniques and methods, the authors are inclined to accept Torpin's hypothesis, which affirms that the initial moment of the series of events which causes the formation of the amniotic bands is the breakage of the amniotic sac.