Antenatal risk prediction of shoulder dystocia: influence of diabetes and obesity: a multicenter study

Purpose To estimate the risk of shoulder dystocia (SD) in pregnancies with/without maternal diabetes or obesity; to identify antenatal maternal and fetal ultrasound-derived risk factors and calculate their contributions. Methods A multicenter retrospective analysis of 13,428 deliveries in three tertiary hospitals (2014-2017) with fetal ultrasound data <= 14 days prior to delivery (n = 7396). Inclusion criteria: singleton pregnancies in women >= 18 years old; vertex presentation; vaginal delivery at >= 37 weeks of gestation. Estimated fetal weight (EFW) and birth weight (BW) were categorized by steps of 250 g. To evaluate risk factors, a model was performed using ultrasound data with SD as the dependent variable. Results Diabetes was present in 9.3%; BMI >= 30 kg/m(2) in 10.4% and excessive weight gain in 39.8%. The total SD rate was 0.9%, with diabetes 2.0% and with obesity 1.9%. These increased with BW 4250-4499 g compared to 4000-4249 g in women with diabetes (12.1% vs 1.9%, P = 0.010) and without (6.1% vs 1.6%, P < 0.001) and at the same BW threshold for women with obesity (9.6% vs 0.6%, P = 0.002) or without (6.4% vs 1.8%, P < 0.001). Rates increased similarly for EFW at 4250 g and for AC-HC at 2.5 cm. Independent risk factors for SD were EFW >= 4250 g (OR 3.8, 95% CI 1.5-9.4), AC-HC >= 2.5 cm (OR 3.1, 95% CI 1.3-7.5) and diabetes (OR 2.2, 95% CI 1.2-4.0). HC/AC ratio, obesity, excessive weight gain and labor induction were not significant. Conclusion Independent of diabetes, which remains a risk factor for SD, a significant increase may be expected if the EFW is >= 4250 g and AC-HC is >= 2.5 cm.