(505) Likelihood of shoulder dystocia in nondiabetic patients with birthweight ≥ 4,000 grams

Objective:
To evaluate the likelihood of shoulder dystocia in neonates ≥4,000 grams when combining excessive gestational weight gain (GWG) with a 1-hour glucose challenge test (GCT) ≥135mg/dL.

Study Design:
This retrospective cohort study included 344 singleton, vaginal deliveries with birthweight ≥4,000 grams to nondiabetic patients at a single institution from 1/1/19-12/31/22. Patients were stratified into 3 risk groups: High (excessive GWG + GCT≥135), Moderate (excessive GWG or GCT≥135), Low (neither). Excessive GWG was defined as more than the upper limit of weight gain for pre-pregnancy BMI by Institute of Medicine guidelines. The primary outcome was shoulder dystocia. Chi-square test and Mantel-Haenszel trend test were used for statistical analysis.

Results:

The overall incidence of shoulder dystocia was 9.0% (31/344). There was a significant trend showing less dystocia as risk decreased: High 15.4% (8/52), Moderate 9.3% (20/215), Low 3.9% (3/77), p=0.02. A larger proportion of Black 18.0% (7/39) and Hispanic 15.6% (7/45) patients had shoulder dystocia compared to White 6.8% (17/251) and Asian (0%), p=0.04. More neonates in the dystocia group had Apgar scores (1 & 5 minutes) < 7 and had higher initial glucose values. A logistic regression model, including race and risk group, revealed the High-risk group was 4 times more likely to have shoulder dystocia compared to the Low-risk group (OR 4.03, 95% CI 1.08-15.00), p=0.04. Compared to White patients, both Black (OR 3.0, 95% CI 1.15-7.61) and Hispanic (OR 2.69, 95% CI 1.06-6.84) patients were almost 3 times as likely to have a shoulder dystocia.

 

Conclusion:

Risk stratification based on excessive GWG + GCT≥135mg/dL in nondiabetic patients successfully identified singleton pregnancies with birthweight ≥4,000 grams that had an increased likelihood of shoulder dystocia, with the High-risk group having over 4-fold increased odds compared to the Low-risk group. This model provides a practical tool for counseling and delivery planning in pregnancies complicated by macrosomia. Prospective validation could further optimize risk thresholds for clinical implementation.