Factors predisposing to perinatal death related to uterine rupture during attempted vaginal birth after caesarean section: retrospective cohort study.

OBJECTIVE To determine the factors associated with an increased risk of perinatal death related to uterine rupture during attempted vaginal birth after caesarean section. DESIGN Population based retrospective cohort study. SETTING Data from the linked Scottish Morbidity Record and Stillbirth and Infant Death Survey of births in Scotland, 1985-98. PARTICIPANTS All women with one previous caesarean delivery who gave birth to a singleton infant at term by a means other than planned repeat caesarean section (n = 35 854). MAIN OUTCOME MEASURES All intrapartum uterine rupture and uterine rupture resulting in perinatal death (that is, death of the fetus or neonate). RESULTS The overall proportion of vaginal births was 74.2% and of uterine rupture was 0.35%. The risk of intrapartum uterine rupture was higher among women who had not previously given birth vaginally (adjusted odds ratio 2.5, 95% confidence interval 1.6 to 3.9, P < 0.001) and those whose labour was induced with prostaglandin (2.9, 2.0 to 4.3, P < 0.001). Both factors were also associated with an increased risk of perinatal death due to uterine rupture. Delivery in a hospital with < 3000 births a year did not increase the overall risk of uterine rupture (1.1, 0.8 to 1.5, P = 0.67). However, the risk of perinatal death due to uterine rupture was significantly higher in hospitals with < 3000 births a year (one per 1300 births) than in hospitals with >or= 3000 births a year (one per 4700; 3.4, 1.0 to 14.3, P = 0.04). CONCLUSION Women who have not previously given birth vaginally and those whose labour is induced with prostaglandin are at increased risk of uterine rupture when attempting vaginal birth after caesarean section. The risk of consequent death of the infant is higher in units with lower annual numbers of births.