Familial occurrence of dystocia

OBJECTIVE: A cohort study was conducted to determine the risk of dystocia for women whose mothers, sisters, or twin sisters had dystocia during childbirth. STUDY DESIGN: A linked database was constructed between 2 separate Swedish birth registries. Obstetric data on mothers giving birth to daughters during the period 1955 to 1972 were studied. Among these daughters, sister-couples and twins were identified. The daughters subsequently became mothers during 1973 and 1990 and obstetric data on the first deliveries were also studied. RESULTS: If a mother had dystocia when delivering her eldest daughter, this daughter had an increased risk of dystocia during her own first childbirth (odds ratio 1.7, 95% confidence interval 1.2 to 2.4). If the mother had an assisted instrumental delivery (vacuum extraction, forceps, or cesarean section) because of dystocia, there was a higher risk for her daughter to have an instrumental delivery because of dystocia (odds ratio 1.8, 95% confidence interval 1.0 to 3.1). Among primiparous sisters the risk of an instrumental delivery because of dystocia in a younger sister was more than tripled (odds ratio 3.5, 95% confidence interval 2.1 to 5.8) if her elder sister had a dystocic labor requiring instrumental intervention. The risk among twins increased more than 20-fold (odds ratio 24.0, 95% confidence interval 1.5 to 794.5) if 1 twin sister had dystocia during her first childbirth. CONCLUSION: Dystocia has a familial occurrence, suggesting a possible genetic factor explaining inefficient uterine action.