[Evaluation of the mechanism of decreased tensile strength of fetal membrane in premature rupture of membrane].

Pathological morphology, thickness, tensile strength, coefficient variation of elasticity and immunohistochemical characteristics of fetal membrane in 246 cases of premature rupture of membrane (PROM) and 30 cases of control were investigated. The results showed that fetal membrane of PROM group appeared to be thinner, mainly composing of chorionic membrane lacking of mature development of fibroid component. The thickness of fetal membrane at the rupture site (54 +/- 11 microns) in PROM group was significantly thinner than that (208 +/- 94 microns) in control. The difference of tensile and elasticity strength of fetal membrane between 2 groups was highly significant. According to the findings of some immunohistochemical indices such as collagen type IV, FN, vimentin, MNF116, hCG and desmin, different component including collagenic fibers, basal membrane, fibroblastic cells, myofibroblastic cells and trophoblastic cells in fetal membrane and villus of PROM group revealed either dysplasia or aging. The mechanism of changes in biophysical characteristics of fetal membrane in PROM caused by noninfectious factors has been evaluated mainly.