Physical properties of the chorioamnion throughout gestation

OBJECTIVE: Our purpose was to assess the tensile strength of the chorioamnion at various gestational ages. STUDY DESIGN: Segments of chorioamnion were obtained from 35 patients delivered at gestational ages ranging from 17 to 41 weeks. Clinical information including gestational age, chorioamnionitis, premature rupture of membranes, and onset of labor was recorded. Tensile strength (grams to burst and deflection at rupture) was measured on 2 to 16 specimens per patient. Tensile strength of several commercial products was used for comparison. RESULTS: Tensile strength increases up to 20 weeks of gestation and then plateaus until 39 weeks of gestation, when it falls dramatically. Clinical chorioamnionitis alone did not affect tensile strength, but gross membrane inflammation resulted in reduced tensile strength. CONCLUSIONS: Tensile strength of the chorioamnion varies with gestational age. This baseline information will be useful in assessing the effects of various conditions and therapies on membrane strength and may provide insight into spontaneous rupture of membranes.