title: Contractions, a risk for premature rupture of fetal membranes: a new protocol with cyclic biaxial tension.
abstract: This study aims at investigating the effect of repeated mechanical loading on the rupture and deformation properties of fetal membranes. Ten membranes delivered by cesarean sections were tested using a custom-built inflation device which provides a multi-axial stress state. For each membrane, a group of samples was first cyclically stretched by application of pressure ranging between 10 and 40 mmHg. After cycles, samples were subjected to inflation up to rupture. Differences between mechanical parameters from cycled and uncycled samples were analyzed. Ten cycles at 40% of mean critical membrane tension--representative of mean physiologic contractions--did not affect strength and stiffness of fetal membranes but reduced the work to rupture, thus indicating that contractions might increase the risk of premature rupture of the membrane. Cyclic testing demonstrated a large hysteresis loop and irreversible deformation on the first cycle, followed by rapid stabilization on subsequent cycles. In 80% of tests, amnion ruptured first and at the periphery of the sample, under uniaxial strain state. Chorion ruptured at higher deformation levels in the middle, under biaxial strain state.
authors.affiliation: Department of Obstetrics, University Hospital Zurich, 8091 Zurich, Switzerland. michela.perrini@usz.ch
authors.forename: Michela
authors.initials: M
authors.lastname: Perrini
authors.forename: Wilfried
authors.initials: W
authors.lastname: Bürzle
authors.forename: Claudia
authors.initials: C
authors.lastname: Haller
authors.forename: Nicole
authors.initials: N
authors.lastname: Ochsenbein-Kölble
authors.forename: Jan
authors.initials: J
authors.lastname: Deprest
authors.forename: Roland
authors.initials: R
authors.lastname: Zimmermann
authors.forename: Edoardo
authors.initials: E
authors.lastname: Mazza
authors.forename: Martin
authors.initials: M
authors.lastname: Ehrbar
mesh_terms: D005321:Extraembryonic Membranes; D005260:Female; D005322:Premature Rupture of Fetal Membranes / Q000209:etiology*; D006801:Humans; D008422:Materials Testing; D011247:Pregnancy; D012306:Risk; D013314:Stress, Mechanical; D014590:Uterine Contraction