[Anaesthesia, a cause of fetal distress?]

To describe the effects of anaesthetic techniques and agents on the risk of fetal distress during labour pain relief and anaesthesia for caesarean section.

Data on obstetric anaesthesia- and analgesia-induced fetal distress were searched in Medline database using MESH terms: fetal distress, anaesthesia, analgesia, labour, caesarean section, and umbilical artery pH. Trials published in English or French language were selected.

Because of their haemodynamic effects, regional anaesthesia and analgesia, especially spinal anaesthesia for Caesarean section, could induce a decrease in umbilical artery pH (UApH). Moreover, intravenous ephedrine, especially when used in large doses can worsen the acidosis. Labour epidural analgesia is associated with a better acid-base balance than systemic analgesia. Experimental studies have demonstrated harmful effects of systemic opioids and hypnotic drugs on UApH and the foetal brain respectively. Clinical implications of these potentially detrimental effects remain to be determined.

All obstetric anaesthesia and analgesia techniques are associated with a theoretical risk of fetal distress, but given the fact that regional anaesthesia techniques are also associated with well-demonstrated benefits for the mother and the newborn, the latter remain the preferred choice in obstetric practice.