Can shoulder dystocia be predicted before operative vaginal delivery using a score that includes ultrasonographic head-perineum distance measurement?

Objective: The main study objective was to develop a novel shoulder dystocia (SD) prediction score using ultrasound-based head-perineum distance measured before an operative vaginal delivery (OVD).

Methods: This retrospective unicentric study (Lille, France) included all cases of OVD of singleton pregnancies from March 2019 to October 2020, with cephalic presentation and > 37 weeks of gestation, for which intrapartum sonography was performed. A multiclass-penalized logistic regression model was used to develop the SD prognostic score, with missing values imputed by multiple imputations.

Results: Among the 1708 patients with OVD, 773 who underwent ultrasound for head-perineum distance were included. SD occurred in 99 cases (12.8%). The SD's predicting factors (and their weights) included the following: maternal age younger than 28 years (3 points); multiparous (4 points); induced labor (4 points); gestational diabetes (3 points); and head-perineum distance without pressure (≤20 mm [-2 points], using 21-30 mm as reference, 31-40 mm [2 points], 41-50 mm [4 points], 51-60 mm [6 points], and >60 mm [8 points]). Three patient risk subgroups were categorized as score range (occurrence percentage) as low risk: < 3 (< 10%), high risk: 3-8 (10%-20%), and very high risk: > 8 (> 20%).

Conclusion: The developed scoring system may help predict SD occurrence during OVD using five delivery room parameters. Replication with other populations and prospective cohorts will be needed for validation.