A scoring system for detection of macrosomia and prediction of shoulder dystocia: a disappointment.

OBJECTIVE: To develop a scoring system for the detection of a macrosomic fetus (birth weight (BW) >or= 4000 g) and predict shoulder dystocia among large for gestational age fetuses. STUDY DESIGN: We retrospectively identified all singletons with accurate gestational age (GA) that were large for GA (abdominal circumference (AC) or estimated fetal weight (EFW) >or= 90% for GA) at >or=37 weeks with delivery within three weeks. The scoring system was: 2 points for biparietal diameter, head circumference, AC, or femur length >or=90% for GA, or if the amniotic fluid index (AFI) was >or=24 cm; for biometric parameters <90% or with AFI <24 cm, 0 points. The predictive values for detection of shoulder dystocia were calculated. RESULTS: Of the 225 cohorts that met the inclusion criteria the rate of macrosomia was 39% and among vaginal deliveries (n = 120) shoulder dystocia occurred in 12% (15/120; 95% confidence interval (CI) 7-20%). The sensitivity of EFW >or=4500 g to identify a newborn with shoulder dystocia was 0% (95% CI 0-21%), positive predictive values 0% (95% CI 0-46%), and likelihood ratio of 0. For a macrosomia score >6, the corresponding values were 20% (4-48%), 25% (5-57%) and 2.3. CONCLUSION: Though the scoring system can identify macrosomia, it offers no advantage over EFW. The scoring system and EFW are poor predictors of shoulder dystocia.