Objective: 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.
Study design: 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).
Results: 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.
Conclusion: Prior shoulder dystocia increased the risk of shoulder dystocia in the second delivery. However, offspring birthweight was by far the most important risk factor.