Deformation and creep in the human chorioamniotic sac.

This paper presents a review of physical principles involved in deformation and creep in the human chorioamniotic membrane. These are definable rheological properties found in many materials. Experimental data are presented on 66 human fetal membranes. A difference in the stress tolerance between preterm and term membranes is demonstrated. A computer model has been devised which allows for the calculation of changes in thickness of the membrane at the point of fracture. This computer model allows for the study of the physical property of the tissue in ways which have not previously been suggested. The model suggests that the pathophysiology related to rupture of the membrane is based on changes in the thickness of this tissue occurring secondary to acute and chronic stress applications. The data derived in these experiments suggest a possible physical model for rupture of the membranes; they also introduce questions regarding the anatomic and biochemical makeup of the chorion and the amnion and the respective role that each plays in maintaining the integrity of the human chorioamniotic sac.