Uterine contractility and oxytocin sensitivity in preterm, term, and postterm pregnancy.

The records of 117 patients who had serial nonstress tests (N = 285) and oxytocin challenge tests (N = 268) were analyzed to determine whether baseline uterine contractility and/or oxytocin sensitivity changed with increasing gestational age. The results obtained in patients who were delivered before, at, and after term were compared. Uterine contractility and oxytocin sensitivity increased in all groups as gestational age progressed. No significant differences in uterine contractility were noted among groups; however, oxytocin sensitivity was significantly increased in the preterm group (p less than 0.001) and decreased in the postterm group (p less than 0.001). Our results suggest that the response of the uterus to oxytocin early in pregnancy may help to identify patients who will be delivered before or after term.