Membrane Status and Reliability of Intrapartum Transperineal Ultrasound in Cervical Dilatation Assessment

Background and Objectives: Labor progression evaluation through repeated vaginal examinations remains the primary method of monitoring in delivery rooms globally. Transperineal intrapartum ultrasound has been shown to be reliable for assessing cervical dilatation, with substantial concordance with digital vaginal examinations. However, none of the analyzed studies investigated the influence of membrane integrity on ultrasound measurements. This study assessed the impact of membrane status on cervical dilatation evaluation via transperineal ultrasound compared to clinical examination, and the extent of agreement based on dilatation level and membrane status. Methods: A nine-month longitudinal observational study was conducted in the Obstetrics and Gynecology Clinic of "Sfântul Pantelimon" Clinical Emergency Hospital (Bucharest, Romania). Patients underwent two clinical examinations and two transperineal ultrasound measurements, one at a dilatation less than 8 cm and the other at a dilatation closer to full dilatation (above 8 cm). Agreement between clinical and ultrasound measurements was analyzed based on membrane integrity and dilatation level. Results: In total, 239 patients were included, and 478 cervical dilatation measurements were obtained. Only the 7-8 cm subgroup exhibited statistically significant differences in accuracy between patients with intact and ruptured membranes. The Pearson correlation results for membrane status were 0.87 (p-value < 0.001) for intact membranes and 0.91 (p-value < 0.001) for ruptured membranes. Both groups show a strong positive correlation, suggesting that ultrasound and clinical measurements tend to increase simultaneously, regardless of membrane status. Conclusions: Transperineal ultrasound is useful for labor monitoring, but its accuracy decreases significantly in advanced labor, especially beyond 8 cm dilatation and in cases with ruptured membranes.