Correlation between Subpubic Arch Angle and Mode of Delivery in Large-for-Gestational-Age Fetuses

Abstract

Objectives: A narrow subpubic arch angle (SPA) has been associated with a higher risk of operative delivery and prolonged labor. The aim of this study was to evaluate the correlation between SPA and labor outcome in a cohort of women delivering a large-for-gestational-age (LGA) fetus. Methods: An observational study involving two Italian tertiary centers (Parma and Rome) was carried out. Nulliparous women referred to the antepartum clinic between 35 and 39 weeks due to an increased risk of having an LGA fetus at birth were prospectively selected for the study purpose. Within the study cohort, SPA measurements were obtained by means of transperineal 3D ultrasound. Elective caesarean section and birth weight below 3,750 g represented exclusion criteria. In the final study group, SPA values were compared between the patients who underwent spontaneous vaginal delivery (SVD) and those who were submitted to unplanned obstetric intervention (UOI) due to prolonged or arrested labor (vacuum delivery or caesarean section). Results: Overall, 129 women were included, and the mean birthweight of the neonates was 4,066 ± 263.03 g. SVD occurred in 63 patients (48.8%), whereas UOI due to prolonged or arrested labor was performed in 66 (51.2%), including 21 cases of vacuum delivery and 45 caesarean sections. The SPA was significantly smaller among women who underwent UOI than in those who achieved SVD (107.9 ± 13.4 vs. 120.7 ± 9.4°, p < 0.001). Furthermore, SPA width was inversely correlated with labor length (p < 0.001). Multivariable logistic regression analysis showed that a smaller SPA (OR 1.091, 95% CI 1.051-1.134, p < 0.001) and an increased birthweight (OR 1.002, 95% CI 1.000-1.004, p = 0.037) were independent risk factors for operative delivery. Conclusion: SPA measurement before labor is helpful in predicting the risk of operative delivery due to prolonged or arrested labor among nulliparous women delivering LGA fetuses.

CADOES: An interactive machine-learning approach for sex estimation with the pelvis

“…Pelvic height is larger in males and suggests that size enacts an essential role in the dimorphic condition of the pelvic region. The broadest subpubic angles observed in female individuals are probably related with obstetrics [58], as obstetric problems, such as labor duration and risk of obstetric intervention due to poor progression, are inversely associated with the breadth of the subpubic angle [59]. Ilium blade length, bispiniatic width and the iliac fossa depth are also among the pelvic variables showing more sexual dimorphism.…”

Pre-Induction Transperineal Ultrasound Assessment for the Prediction of Labor Outcome

“…Another limitation relates to the fact that we did not evaluate the measurement of transperineal subpubic angle and fetal head circumference in our study. Both parameters have been shown to be useful in predicting unplanned operative delivery before IOL in nulliparous women [27,28].…”

Sonographic Risk Assessment for An Unplanned Operative Delivery: A Prospective Study

“…The angle of progression, widely reported in the literature as a predictive measurement when obtained before the onset of labor, during the rst and second stages of labor, and before assisted delivery, represents the fetal head station. The pubic arch angle (PAA), reported by our group [24][25] and others [26][27][28][29][30][31][32][33] to have a strong negative correlation with persistent occiput posterior and mode of delivery, represents the primary pelvimetric diameter of the pelvic outlet. Interestingly, some of these parameters are prone to modi cation by other parameters, such as maternal age [4].…”