The effect of epidural anaesthesia for caesarean section on maternal uterine and fetal umbilical artery blood flow velocity waveforms.

The blood flow resistance in the maternal uteroplacental and fetal umbilical artery circulation was studied in eight otherwise normal patients undergoing elective lower segment caesarean section. The systolic/diastolic A/B ratio (the ratio of peak systolic to least diastolic flow velocity) for the uteroplacental and fetal umbilical circulation was determined from the artery blood flow velocity-time waveform and used as an index of blood flow resistance. Each patient received a 1 litre intravenous crystalloid infusion before an epidural bupivicaine injection. Both crystalloid infusion and epidural anaesthesia resulted in a significant decrease in the maternal uteroplacental systolic/diastolic (A/B) ratios, associated with a decrease in fetal umbilical artery A/B ratio. This study suggests a beneficial fetal effect from the improved maternal uterine perfusion after epidural anaesthesia.