Background Clinical assessment of fetal head station is difficult and subjective; it is mandatory before attempting operative vaginal delivery. Objective The principal objective of our study was to assess whether measurement of the perineum-to-skull ultrasound distance was predictive of a difficult operative vaginal delivery. Secondary objectives included evaluation of the interobserver reproducibility of perineum-to-skull ultrasound distance and comparison of this measurement and digital examination in predicting a difficult operative delivery. Study Design This was a prospective cohort study including all cases of operative vaginal deliveries in singleton pregnancies in cephalic presentation >34 weeks’ gestation, from 2012 through 2015. All data were entered prospectively in a medical record system specially devised to meet the requirements of this study. Results Of the 659 patients in whom perineum-to-skull ultrasound distance was measured prior to operative vaginal delivery, 120 (18%) met the composite criterion for a difficult extraction. Perineum-to-skull ultrasound distance measurement of ≥40 mm was significantly associated with the occurrence of a difficult extraction based on the composite criterion, after adjustment for parity, presentation type, and fetal macrosomia (odds ratio, 2.38; 95% confidence interval, 1.51–3.74; P = .0002). The intraclass correlation coefficient between the perineum-to-skull ultrasound distance measured by the first operator and that measured by the second operator was 0.96 (95% confidence interval, 0.95–0.97; P <.0001). Based on the receiver operating characteristic curve analyses, perineum-to-skull ultrasound distance was a more accurate predictor of difficult operative delivery than digital vaginal examination (P =.036). Conclusion Measurement of the perineum-fetal skull ultrasound distance is a reproducible and predictive index of the difficulty of instrumental extraction. Ultrasound is a useful supplementary tool to the usual clinical findings.
Kasbaoui, S., Séverac, F., Aïssi, G., Gaudineau, A., Lecointre, L., Akladios, C., … Sananès, N. (2017). Predicting the difficulty of operative vaginal delivery by ultrasound measurement of fetal head station. In American Journal of Obstetrics and Gynecology (Vol. 216, pp. 507.e1-507.e9). Mosby Inc. https://doi.org/10.1016/j.ajog.2017.01.007