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

Abstract

Uterine activity was studied during labor 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/15 min was maintained at between 700-1500 kPa [kilopascals] or at between 1500-2000 kPa, 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. The uterus must achieve a certain total uterine activity in induced labor which is best achieved by maintaining optimal uterine activity levels of 1500-2000 kPa/15 min to effect vaginal delivery of the baby in good condition in optimal time.