Correlation of head-to-body delivery intervals in shoulder dystocia and umbilical artery acidosis

Abstract

Objective: Our goal was to determine the effect of shoulder dystocia on umbilical artery acidosis. Study Design: We performed a retrospective analysis of 134 mother-infant pairs of shoulder dystocia cases at our institution from January 1, 1994, through December 31, 1997. Cases were identified from the obstetric database, and charts were abstracted for demographics, head-to-body delivery interval, umbilical blood gas parameters, and neonatal outcome. Pooled student t tests were used to compare mean blood gas values with data previously reported from our patient population. Regression analysis was performed regarding head-to-body delivery interval and blood gas parameters. Results: The mean umbilical artery pH of shoulder dystocia cases (7.23 ±.082) was less than the mean arterial pH of all vaginal deliveries in our institution (7.27 ±.069), P <.001. Head-to-body delivery intervals (available for 44 cases) were not associated with statistically significant alterations in umbilical artery pH (r2 =.0004), PCO2 (r2 =.011), or base deficit (r2 =.006). Increasing head-to-body delivery interval was also not significantly correlated with decreasing 5-minute Apgar score (r =.0278). Conclusion: In our study population, shoulder dystocia resulted in statistically significant but clinically insignificant reductions in mean umbilical artery blood gas parameters. No statistically significant linear relationship was identified between the head-to-body delivery interval and fetal acid-base status. (Am J Obstet Gynecol 2001;185:268-74.)