Uterine hyperstimulation is a possibility when oxytocin is used to induce and augment labor. Unless the process is reversed, uteroplacental perfusion may decline; among the sequelae are fetal decelerations, bradycardia, placental abruption, and uterine rupture. Decreasing or discontinuing the oxytocin and taking appropriate resuscitative measures are effective in a large majority of cases but entail significant delay. This study was intended to show whether adding terbutaline to oxytocin will hasten the resolution of hyperstimulation without increasing the risk of fetal side effects.
Twenty-nine women with singleton term pregnancies who were in active labor and receiving oxytocin, and in whom uterine hyperstimulation had been present for at least 20 minutes, were enrolled in the study. Markers of hyperstimulation included 20 minutes or more of tachysystole, hypertonus, tetany, and couplet or triplet contractions. Fifteen women were randomly assigned to receive 250 μg terbutaline subcutaneously with no change in the oxytocin dose. The dose was repeated twice if hyperstimulation remained present after 15 and 30 minutes. In control women, oxytocin infusion was discontinued and then restarted at half the initial dose if contractility became normal within 30 minutes. If necessary, oxytocin was restarted at a rate of 2 mIU/minute. The 2 groups were comparable in age, rate oxytocin infusion, cervical dilatation, the need for cesarean section, chorioamnionitis, and Apgar scores.
All women in the study group and 47% of those managed conventionally no longer experienced hyperstimulation within 15 minutes. The average times to resolution were 9 and 35 minutes, respectively. Hyperstimulation recurred in 5 control women and 3 women in the study group. The interval from intervention to return of a normal contraction pattern did not differ between the 2 groups. No significant differences were noted in the frequency of chorioamnionitis or the need for operative delivery. In no case in either group was the umbilical cord blood pH less than 7.0 or the 5-minute Apgar score lower than 7.
Administering terbutaline while continuing oxytocin appears to be more effective than withdrawing oxytocin in relieving uterine hyperstimulation during labor. Rapid improvement may be especially helpful when vaginal delivery is attempted after past cesarean section or in multiple pregnancies.