Intact fetal membranes. Morphological predisposal to rupture

Samples from different parts of the fetal membranes were examined by both light and transmission electron microscopy. Samples were obtained during elective cesarean section after full-term normal pregnancy. The results indicated that the different layers of the membranes had undergone ultrastructural changes varying according to the site from which the sample was taken. Samples taken from areas geometrically opposite to the placenta showed evidence of tension on the amniotic epithelium and disruption of the basement membrane. Samples taken from the area covering the internal os showed changes in the collagenous material. The implications of these findings are discussed.