[The influence of pethidine on uterine activity and dilatation of the cervix in spontaneous labour (author's transl)].

Two series of patients, randomly selected, 29 of whom had pethidine and 29 of whom had a placebo, were compared in order to study the influence of intra-muscular pethidine on uterine activity and on the speed with which the cervix dilated. The experiment was a double blind one. A significant increase in the basal tone of the uterine muscle was found 40 minutes after the injection in the group that received pethidine, although there was no other significant difference in the other parameters which were intensity, frequency, length, surface of the contractions [half the height multiplied by (X times) the base on the monitor recording], uterine activity in Montevideo and in Toulouse units and the speed of dilatation. These results do not bear out the classical hypotheses of the muscle relaxing effect of pethidine, and in particular that the uterus relaxes better between contractions, nor that there is relaxation of the cervix in labour. The indication for the use of pethidine is perhaps justified because of its analgesic effect, but as far as favouring dilatation of the cervix in labour is concerned is at best worthy of discussion.