Intrauterine pressure wave characteristics of the upper and lower uterine segments in parturients with active-phase arrest

Objective: To determine the gradient of pressure between the upper and the lower uterine segments of parturients with non-progressing labor and to see whether the gradient correlates with subsequent successful oxytocin augmentation. Methods: Fifteen women with active-phase arrest of labor were monitored with two intrauterine pressure transducers before and after oxytocin augmentation. Seven parturients without arrest of labor were evaluated for comparison. One intrauterine pressure transducer was inserted into the upper and one into the lower uterine segment of each subject. Overall, 444 contractions were assessed using the mean active pressure method. Results: A total of 16 patients delivered vaginally. Nine received oxytocin augmentation, and all had significantly higher pressure in the upper segment than in the lower both before and after oxytocin (P <.001). Six women delivered by cesarean had a reversed gradient of uterine activity, with the lower segment contracting significantly more strongly than the upper uterine segment both before (P =.002) and after oxytocin (P =.001). Conclusion: Pressure gradients between the upper and lower uterine segments in the active phase might predict the likelihood of success of oxytocin augmentation.