Fetal membranes from term vaginal deliveries have a zone of weakness exhibiting characteristics of apoptosis and remodelling. J Soc Gynecol Invest

BACKGROUND: Recently we identified a weak zone in term, pre-labor (repeat Cesarean section) human fetal membranes (FMW) overlying the cervix with biochemical characteristics suggestive ofapoptosis and collagen remodeling. We stggested that this weak zone is the F1M rupture initiation site. Vaginally delivered patients have a weak zone in their FM ' overlying the cervix; a comparable weak zone lies adjacent to the tear line in FM after spontaneous rupture (SROCM). METHODS: FMed from vaginally delivered patients with artflcial rupture (AROA/I) and SROM were collected. FMI ofAROM patients were marked per vagina to identify the FiMl zone overlying the cervix. Postpartum FAMI were cut, strength tested, and piece strengths were remapped to their former location on a three-dimensional model. A 10-cm diameter zone centered on the marked area (AROM), or defined weak zone (SROM,) was compared with the remaining Fill. RESULTS: AROA'I FM.W exhibit a para-cervical weak zone. SROM 'Fed exhibit a comparable zone on the tear line. Tie mean rupture strength within weak zones was 60 % of the remaining membranes (P <.001). AROM and SROMFAI I weak zones both exhibit increased matrix metalloproteinase 9, increased poly (ADP-ribose) polymnerase I cleavage, decreased tissue inhibitor of metalloproteinase 3 protein, and histology consistent with remodeling and apoptosis. CONCLUSION: V aginally delivered AROM FMi contain a weak zone overlying the cervix. Vqqaginally delivered SROGA FM contain a weak zone adjacent to the tear line that exhibits biochemical andi mechanical characteristics suggestive of collagen remodeling and apoptosis comparable to those of the AR FM weak zone