Are labor abnormalities more common in shoulder dystocia?

OBJECTIVE: Our objective was to determine the asociation between labor abnormalities and shoulder dystocia. STUDY DESIGN: All consecutive cases of shoulder dystocia from January 1986 to August 1994 were reviewed (n = 276). For purposes of comparison a control group of vaginally delivered patients was randomly selected in a 2:1 ratio (n = 600). Charts were reviewed for demographic information, labor and delivery events, and neonatal outcome. RESULTS: Labor abnormalities were comparable in the shoulder dystocia and control groups, both in the active phase and in the second stage. When patients with diabetes and those with macrosomic infants were analyzed separately, no significant differences in labor abnormalities were identified. The rate of operative vaginal delivery was significantly higher in the shoulder group, and one third of the operative deliveries were midpelvic. In addition, the induction rate was higher in the shoulder group. CONCLUSIONS: Our data suggest that labor abnormalities may not serve as clinical predictors for subsequent development of shoulder dystocia, thus emphasizing the unpredictability of this condition.