The association between a previous uneventful vaginal delivery of a macrosomic neonate and future shoulder dystocia

To examine the association between vaginal delivery of a previous macrosomic neonate (birthweight (BW)≥ 4000) among non-diabetic women and the rate of shoulder dystocia (SD) in the subsequent pregnancy.

A historical prospective cohort study in a university affiliated medical center from 2005 to 2019. Women who had a singleton pregnancy and two consecutive deliveries in our medical center were included. Women with previous GDM, SD or cesarean delivery were excluded. Univariate analysis was followed by multivariate logistic regression.

A total of 38,942 women were included. SD incidence among the subsequent pregnancies was 0.44 % (172 women). In univariate analysis women with previous delivery of large neonates: BW≥90th percentile for gestational age and BW ≥ 4000 g had higher risk for subsequent SD (odds ratio 2.69 [95 % confidence interval 1.89-3.84], p < 0.01 and 2.71 [1.66-4.44], p < 0.01, respectively). However, a backward stepwise multivariate logistic regression model adjusted for significant confounders for SD in the univariate analysis, showed that women with a previous delivery of macrosomic neonate ≥4000 g were not found to have higher or lower risk for SD in the subsequent delivery.

Previous uneventful delivery of a macrosomic neonate to a non-diabetic mother should not be regarded as a risk factor for SD in the subsequent delivery.