Total uterine activity in induced labour--an index of cervical and pelvic tissue resistance.

Uterine activity was studied during labour induced using an automatic infusion system (AIS) or a peristaltic infusion pump (IVAC) to administer oxytocin. In the 110 patients who achieved vaginal delivery the total uterine activity required to effect full dilatation of the uterine cervix was found to vary according to parity and cervical score but not according to mode of oxytocin infusion. Irrespective of whether the uterine activity level per 15 min was maintained at between 700 and 1500 kPas or at between 1500 and 2000 kPas, the total uterine activity was similar the lower levels being compensated for by a longer duration. Fetal outcome, in terms of 1- and 5-min Apgar scores and umbilical vein blood pH, was unaffected by the level of uterine activity. The cervical and pelvic tissue resistance varies according to parity and cervical score and the uterus has to achieve a certain total uterine activity in induced labour which is best achieved by maintaining optimal uterine activity levels of 1500-2000 kPas/15 min to effect vaginal delivery of the baby in good condition in optimal time.