[Rheobase, pelvic score and oxytocin sensitivity test before spontaneous onset of labour (author's transl)].

Electrodiagnostical investigations measuring the rheobase and chronaxy as well as Oxytocin Sensitivity Tests (OST) and estimations of the pelvic score have been carried out on 19 healthy pregnant women from the 34th week on weekly and in daily intervals 1 week before the calculated date of delivery. Generally there was no trend to a decrease of rheobase until 2 days before delivery, whereas a significant drop was found between day -2 and the day of the onset of labour. At the same time the pelvic score ascended highest, but in individual cases there was no direct correlation between pelvic score and rheobase value. The OST became positive in more than 50% before the rheobase decline. Practical aspects of the combined estimation of pelvic score, OST and rheobase are discussed especially in view of the elective induction.