Objective: The objective of the study was to assess the role of uterine activity on fetal outcome. Study Design: Intrauterine pressure (IUP) recordings from consecutive term singleton, vaginal deliveries collected between June 1, 1993, and July 1, 2004, were analyzed. One thousand four hundred thirty-three recordings were included. IUP data were obtained using HP 8040A and HP M1350 cardiotocographs. For each recording the uterine contraction curve was analyzed, and the following contraction parameters were determined: relaxation time; contraction duration, frequency, amplitude, and surface; Montevideo units; and active planimeter units and contraction frequency. IUP recordings and contraction parameters from deliveries ending with an umbilical artery pH of 7.11 or less were compared with those ending with an umbilical artery pH of 7.12 or greater. Statistical analyses were performed using Student's t test and logistic regression. Results: An umbilical artery pH 7.11 or less at birth is associated with significant more uterine activity during the first and second stage of labor. Conclusion: Increased uterine activity is significantly associated with a higher incidence of an umbilical artery pH of 7.11 or less.