Risk of shoulder dystocia in second delivery: does a history of shoulder dystocia matter?

Abstract

Our aim was to estimate the relative and absolute risk of shoulder dystocia in the second delivery according to history of shoulder dystocia and offspring birthweight. A retrospective cohort study including all women in Norway with 2 consecutive singleton vaginal deliveries with fetus in cephalic presentation, during the period 1967-2005 (n = 537,316). In the second delivery shoulder dystocia occurred in 0.8% of all women. In women with a prior shoulder dystocia the recurrence risk was 7.3%. Most cases of shoulder dystocia in second delivery were in women without such history (96.2%). Offspring birthweight was the most important risk factor for shoulder dystocia in second delivery: crude odds ratio, 292.9 (95% confidence interval, 237.8-360.7) comparing birthweight > 5000 g with 3000-3499 g. Prior shoulder dystocia increased the risk of shoulder dystocia in the second delivery. However, offspring birthweight was by far the most important risk factor.