From so far unknown reasons sometimes one membrane of the gestational sac (amnion) ruptures during the early gestation. Because amnion and chorion practically never fuse, the part of the amnion loosely floats in the uterine cavity, so called amniotic bands. The surface uncovered by the amnial epithelium is “sticky” and easily attaches to the surface of the developing embryo or fetus. By following traction, retraction and winding of the bands around the fetus body during its movments a serious malformations, mutilations of the face, head and body and limbs amputations occur.
Does not happen again in the next gravidity.