High birth weight, induction boosted shoulder dystocia risk.(Obstetrics)

PHOENIX, ARIZ. -- Rates of several traditional obstetric risk factors for shoulder dystocia, such as maternal diabetes, epidural use, and multiparity, were not significantly higher among shoulder dystocia cases than among normal births in a retrospective review of more than 250,000 vaginal births.

High birth weight, however, remained a leading risk factor for shoulder dystocia, Joseph Ouzounian, M.D., reported at the annual meeting of the Pacific Coast Obstetrical and Gynecological Society.

The study included 267,228 vaginal births that took place between 1991 and 2001 at a 10-hospital Kaiser Permanente system in Southern California. During that period 1,686 cases (0.6%) of shoulder dystocia were reported, said Dr. Ouzounian, chief of obstetrics and gynecology and director of maternal/fetal medicine at Kaiser Permanente, Baldwin Park, Calif.

Rates of maternal diabetes and vacuum or forceps use were not significantly different between the shoulder dystocia and no shoulder dystocia groups. Rates of oxytocin use (14.4% vs. 10.4%, respectively) and labor induction (24.5% vs. 16.9%, respectively) were higher in the shoulder dystocia group, however. These differences between groups were statistically significant.

The standout statistic, however, was birth weight, with 19.3% of shoulder dystocia cases associated with a birth weight of more than 4,500 g, compared with 1.5% of non-shoulder dystocia cases.

A total of 56% of shoulder dystocia cases were associated with a birth weight of more than 4,000 g, compared with 9.6% of non-shoulder dystocia cases.

"We saw a striking difference in birth weight, with about a 15-fold difference between the shoulder dystocia group and non-shoulder dystocia group," Dr. Ouzounian said.