Neonatal head circumference to maternal mid‐transverse pelvic distance ratio as a key anatomical predictor for dystocia: Retrospective case–control study

Abstract

AbstractObjectiveThis study aimed to examine maternal and neonatal factors in cesarean deliveries due to dystocia, including cephalopelvic disproportion, latent‐phase prolongation, and fetal malposition or malpresentation. Additionally, we sought to compare the differences between the dystocia subgroups.Method and MaterialsThis retrospective case–control study included women who delivered between January 2010 and June 2021 after 37 weeks of pregnancy and underwent abdominal‐pelvic CT scans within 5 years before and after delivery. Neonatal factors were extracted from medical charts immediately after delivery.ResultsAmong the 292 women studied, those with cesarean deliveries for dystocia were older (mean ± SD, 34.2 ± 4.27 vs. 32.2 ± 3.8, p‐value = 0.002), had higher pre‐pregnancy BMI (22.7 ± 3.67 vs. 21.4 ± 3.48, p‐value = 0.012) and term‐BMI (27.4 ± 3.72 vs. 25.9 ± 3.66, p‐value = 0.010), shorter interspinous distance (ISD, the distance between ischial spine) (10.8 ± 0.76 vs. 11.2 ± 0.85 cm, p‐value = 0.003), and longer head circumference (HC) (35 ± 1.47 vs. 34.4 ± 1.36 cm, p‐value = 0.003) compared to those who had vaginal deliveries. Univariate logistic regression for dystocia revealed associations between HC/maternal height and HC/ISD ratios (OR, 2.02 [95% confidence interval, CI, 1.4 ~ 2.92], 12.13 [3.2 ~ 46.04], respectively). Multivariate logistic analysis indicated that maternal age, ISD, and HC were significant factors for dystocia (OR, 1.11 [95% CI, 1.01 ~ 1.21], 0.49 [0.26 ~ 0.91], 1.53 [1.07 ~ 2.19], respectively). The subgroup with latent‐phase prolongation exhibited the lowest birthweight/term‐BMI ratio (124 ± 18.8 vs. 113 ± 10.3 vs. 134 ± 19.1, p‐value = 0.013).ConclusionThe HC/ISD ratio emerged as a crucial predictor of dystocia, suggesting that reducing term‐BMI could potentially mitigate latent‐phase prolongation. Further research assessing the maternal mid‐pelvis during pregnancy and labor is warranted, along with efforts to reduce BMI during pregnancy.