Trends in the rate of shoulder dystocia over two decades

Objective. To describe the trend in the rate of shoulder dystocia over twenty-four years and identify the risk factors related to the occurrence of dystocia. Methods. Data was obtained from Maryland State regarding all vaginal deliveries that occurred during six different time periods at five-year intervals since 1979. Trends in the rate of shoulder dystocia, episiotomy, forceps and vacuum delivery were examined. Results. There were a total of 277 974 vaginal deliveries. The overall rate of shoulder dystocia was 1.29% (n = 3590). Induction of labor (adjusted OR 1.2, 1.1-1.3), presence of diabetes (gestational (OR 1.9, 1.7-2.3) or pre-gestational (OR 3.8, 2.7-5.4)), fetal macrosomia (OR 5.1, 4.1-6.3) use of episiotomy (OR 1.6, 1.5-1.8), forceps (OR 1.3, 1.0-1.8) or vacuum (OR 2.3, 2.0-3.9) at delivery were associated with a higher rate of shoulder dystocia. Trend. There was an increase in the rate of shoulder dystocia from 0.2% in 1979 to 2.11% in 2003. In addition there was a drop in the overall episiotomy rate from 73.67% to 23.94% and increase in the use of vacuum from 0.1% to 8.36%. Conclusion. The rate of shoulder dystocia has increased by 10 fold during the study period. The use of episiotomy either at spontaneous delivery or instrumental delivery does not appear to decrease the occurrence of shoulder dystocia.