A double blind quantitative study of the effects of meptazinol and pethidine on the fetal heart rate in labour

SummaryA double blind controlled trial was carried out to measure the effects of pethidine and meptazinol on the fetal heart rate in labour. Patients who selected epidural or inhalational analgesia were used as controls.The fetal heart rate was analysed numerically, using a microcomputer, for 45-60 min before and after drug administration to allow for fetal behavioural state changes. Controls showed no change in heart rate or its variation over two successive periods of observation.The mean numbers of accelerations (> 10 beats per min and 15 s duration) were reduced by 46 per cent (P < 0.001) with pethidine administration and by 33 per cent (p < 0.05) with meptazinol. The reduction in overall fetal heart rate variation with pethidine was only 20 per cent (P < 0.05); no change was demonstrated with meptazinol.The mean umbilical artery pH at delivery was 7.28 in the meptazinol babies, higher than the mean of 7.22 in the controls (P<0.05), but no other differences in the blood gas values were found.