[Importance of oxytocin sensitivity for the spontaneous onset of human labor]

The significance of oxytocin for the onset of labour in humans is disputed, mainly because there is no increase in oxytocin concentration in the peripheral maternal blood before onset of labour. However, Fuchs et al. have recently shown that the concentration of oxytocin receptors in the myometrium is significantly higher directly before onset of labour than at the onset of spontaneous contractions. To establish a correlation with the clinical sensitivity to oxytocin, the authors determined the oxytocin sensitivity by means of intravenous administration of 3 X 10 m I.U. of oxytocin with continuous tocographic recording. Parallel to this determination, the cervical score was measured according to Bishop. The patients were 26 healthy pregnant women in whom both parameters were determined daily until onset of spontaneous labour pains. The sensitivity to oxytocin increased significantly during the last few days before spontaneous onset of labour. On the day before onset of pains, almost all of the pregnant women showed maximum sensitivity to oxytocin. Parallel to this, the cervical, scores also increased; on the day before onset of labour pains, almost all pregnant women had a cervical score of 5 or more than 5. On the basis of these results, which concur accurately with the results of measurement of oxytocin receptor concentrations, it is definitely possible to refute the arguments that oxytocin is irrelevant for the onset of labour because its concentration in the maternal plasma does not increase before the pains begin.(ABSTRACT TRUNCATED AT 250 WORDS)