Shoulder dystocia and composite adverse outcomes for the maternal-neonatal dyad

Abstract

Although the neonatal morbidity associated with shoulder dystocia are well known, the maternal morbidity caused by this obstetrical emergency is infrequently reported. This study aimed to assess the composite adverse maternal and neonatal outcomes among vaginal deliveries (at 34 weeks or later) with and without shoulder dystocia. This is a secondary analysis of the Consortium of Safe Labor, an observational obstetrical cohort of all vaginal deliveries occurring at 19 hospitals (from 2002-2008) and for which data on the occurrence of shoulder dystocia were available. The composite adverse maternal outcome included third- or fourth-degree perineal laceration, postpartum hemorrhage (>500 cc blood loss for a vaginal delivery and >1000 cc blood loss for cesarean delivery), blood transfusion, chorioamnionitis, endometritis, thromboembolism, admission to intensive care unit, or maternal death. The composite adverse neonatal outcome included an Apgar score of <7 at 5 minutes, a birth injury, neonatal seizure, hypoxic ischemic encephalopathy, or neonatal death. A multivariable Poisson regression was used to estimate the adjusted relative risks with 95% confidence intervals. The area under the receiver operating characteristic curve was constructed to determine if clinical factors would identify shoulder dystocia. Of the 228,438 women in the overall cohort, 130,008 (59.6%) met the inclusion criteria, and among them, shoulder dystocia was documented in 2159 (1.7%) cases. The rate of composite maternal morbidity was significantly higher among deliveries with shoulder dystocia (14.7%) than without (8.6%; adjusted relative risk, 1.71; 95% confidence interval, 1.64-2.01). The most common maternal morbidity with shoulder dystocia was a third- or fourth-degree laceration (adjusted relative risk, 2.82; 95% confidence interval, 2.39-3.31). The risk of composite neonatal morbidity with shoulder dystocia (12.2%) was also significantly higher than without shoulder dystocia (2.4%) (adjusted relative risk, 5.18; 95% confidence interval, 4.60-5.84). The most common neonatal morbidity was birth injury (adjusted relative risk, 5.39; 95% confidence interval, 4.71-6.17). The area under the curve for maternal characteristics to identify shoulder dystocia was 0.66 and it was 0.67 for intrapartum factors. Although shoulder dystocia is unpredictable, the associated morbidity affects both mothers and newborns. The focus should be on concurrently averting the composite morbidity for the maternal-neonatal dyad with shoulder dystocia.