Predicting the difficulty of operative vaginal delivery by ultrasound measurement of fetal head station

• Published in: American journal of obstetrics and gynecology 2017-05, Vol.216 (5), p.507.e1-507.e9
• Main Authors: Kasbaoui, Sidi, MD, Séverac, François, MD, Aïssi, Germain, MD, Gaudineau, Adrien, MD, MPH, Lecointre, Lise, MD, Akladios, Chérif, MD, PhD, Favre, Romain, MD, PhD, Langer, Bruno, MD, Sananès, Nicolas, MD, MPH
• Format: Article
• Language: English
• Subjects: Adult; Biotechnology; Birth Weight; Cohort Studies; Female; Fetus; Head - diagnostic imaging; head station; Humans; Labor Presentation; Life Sciences; Likelihood Functions; Obstetrical Forceps; Obstetrics and Gynecology; operative vaginal delivery; Parity; Perineum - diagnostic imaging; Predictive Value of Tests; Pregnancy; Ultrasonography, Prenatal; ultrasound; Vacuum Extraction, Obstetrical
• ISSN: 0002-9378; 1097-6868
• DOI: 10.1016/j.ajog.2017.01.007

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.