Urinary bladder distention: effect on labor and uterine activity.

To study quantitatively the effect of urinary bladder distention on labor and uterine activity, 68 patients requiring catheterization were studied. All patients were in the active phase of labor and had transcervical intrauterine pressure monitoring. Patients were studied in the same lateral position for 30 minutes before and after a catheterization interval, during which time uterine activity units were quantitated on line and changes were noted in cervical dilation and station and contraction frequency and tonus. Results were analyzed for the entire study group, for individual patients, and by urine volumes (10 to 550 ml) obtained at catheterization. Total uterine activity units increased in 43 patients and decreased in 25 after catheterization, but when compared with expected increases calculated from the slopes of the precatheterization interval in individual patients, there were 36 increases and 32 decreases. Individual slopes of uterine activity increased in 36 and decreased in 31 cases. There were no differences when the data were analyzed by urine volume, parity, or bith weight except possibly at large volumes. Changes in rates of cervical dilation and descent of the presenting part conform to the expected normal labor pattern. Within the limits of this study, emptying the urinary bladder has no effect on the course of labor or uterine activity based on the dynamic model of labor.