Influence of clinical risk factors for preterm premature rupture of membranes (PPROM) on the elastic strength of fetal membranes at term: A prospective study

Introduction: Premature rupture of membranes (PROM) before 37 weeks of gestation is a common obstetrical event, whose pathophysiology is still poorly understood. Our objective was to study the mechanical strength of fetal membranes in women with a clinical risk factor for preterm premature rupture of membranes (PPROM). Methods: We included, in a prospective, descriptive, single-center study, patients scheduled for cesarean section at term (≥ 37 weeks of gestation). For each patient, we performed uniaxial tensile tests on fetal membranes with a universal testing machine equipped with a force sensor (EZ20®, Lloyds), allowing the recording of an applied force/time curve. We collected maximum force (Fmax), maximum stress (σMax), and Young’s modulus of elasticity. The thickness of each membrane sample was also measured. We compared the values obtained according to certain clinical risk factors for PPROM such as age, body mass index, gravidity, parity, a history of PPROM or preterm birth, smoking, gestational diabetes, geographic origin, and socioeconomic level. Results: We analyzed 31 patients and found no association between the studied risk factors and σMax. Fmax was lower in primiparous patients (p = 0.02) but increased with patient parity (p = 0.005). Gestational diabetes was associated with a higher Fmax (p = 0.033) and sub-Saharan geographical origin with a greater thickness (p = 0.0043). As membrane thickness increased, σMax (p = 0.009) and Young’s modulus decreased (p = 0.037). Conclusion: Primiparous patients have lower membrane mechanical strength than patients who have had one or more deliveries. Mechanically, the thicker membranes are less rigid and less resistant.