[Residual slowing of the heart in the first stage of labour. The interpretation and the prognostic value of this sign (author's transl)].
117 deliveries in which fetal heart slowing was accompanied by residual bradycardia where at least one measure of the fetal pH was undertaken (212 measures were carried out in the whole series) allowed the authors to analyse the maximum and residual amplitudes, the regular or irregular morphology. The frequency of the slowing and its relationship to uterine contractions (regular or variable) and the number of episodes of slowing were recorded before any measures of the fetal pH in utero were undertaken. The regular morphology and the size of the residual degree of bradycardia beyond 30 Bpm are of great diagnostic importance. In fact, while slowing with residual bradycardia below 30 Bpm is tolerable, beyond this 19% of cases show fetal acidosis when slowing is irregular or variable, and 76% when slowing is regular (53 of these had severe acidosis with a pH of less than 7.20). In this last group, which is by far the most dangerous, acidosis appeared after 5 episodes of slowing and became constant after more than 10 episodes. Because of this, measuring pH in the presence of residual slowing would seem to be only useful in irregular types of slowing.