Intrauterine pressure studies in multigravid patients in spontaneous labour: effect of oxytocin augmentation in delayed first stage.
Uterine activity was assessed by measuring the uterine activity integral (UAI) in 116 black multigravid patients in spontaneous active labour at term. Although individual patients showed a wide range of mean UAI levels, normal labour (group I, n = 54) was associated with a mean UAI level of 1640 kPas/15 min which was higher than the mean level observed in patients in whom delay in cervical dilatation occurred in active labour. The patients who failed to progress in labour were treated with oxytocin infusion and 32 of them made good progress in labour and achieved vaginal delivery (group IIa: mean UAI pre-oxytocin treatment 1040 (SD 424) kPas/15 min, post-oxytocin 1890 (SD 559) kPas/15 min). The other 23 patients required operative delivery (group IIb) despite correction of uterine activity after oxytocin treatment (pre-oxytocin mean UAI 1230 (SD 570) kPas/15 min, post-oxytocin 1815 (SD 650) kPas/15 min). The rate of oxytocin infusion varied between patients from 2 to 16 mU/min but in 75% uterine activity was corrected to normal levels by a dose of less than or equal to 8 mU/min. It is concluded that delay in progress in labour is associated with lower intrauterine pressures than are present in normal labour, and that management of patients presenting with inefficient uterine action may benefit from the use of uterine activity integral measurements.