Shoulder dystocia is a potential cause of serious birth injuries, in particular, brachial plexus injuries. Fortunately, it occurs relatively infrequently, but it is challenging to predict. Previous studies have identified several risk factors associated with primary shoulder dystocia, but no studies have examined risk factors for recurrent shoulder dystocia with birth injuries in a subsequent pregnancy.
The aim of this population-based retrospective cohort study was to investigate risk factors for birth injury in a subsequent vaginal delivery among mothers who had a previous delivery complicated by a shoulder dystocia. Data for the years 1987 to 2007 were obtained from the Washington State Longitudinal Birth Database. Multiple logistic regression analysis was used to assess risk factors associated with subsequent birth injuries in a subsequent pregnancy, adjusting for confounding variables.
Birth injuries occurred in 2.4% (223/9232) of the infants born to mothers with a subsequent vaginal delivery who had a previous delivery complicated by shoulder dystocia. Multivariable analysis showed that significant risk factors for birth injury in a subsequent pregnancy among women with shoulder dystocia in an index delivery were birth weight ≥4000 g (adjusted odds ratio [aOR], 4.4; 95% confidence interval [CI], 3.0–6.3), gestational diabetes (aOR, 1.9; 95% CI, 1.2–3.2), Hispanic ethnicity (aOR, 1.9; 95% CI, 1.2–2.9), and maternal obesity (aOR, 1.8; 95% CI, 1.3–2.6).
These findings suggest that the risk factors for birth injury from recurrent shoulder dystocia identified in this study should be considered before deciding on route of delivery in a subsequent pregnancy.