• C Olofsson, A Ekblom, G Ekman-Ordeberg, A Hjelm, and L Irestedt.
• Department of Anaesthesiology and Intensive Care, Karolinska Hospital, Stockholm, Sweden.
• Br J Obstet Gynaecol. 1996 Oct 1;103(10):968-72.

ObjectiveTo evaluate the true analgesic effect of morphine and pethidine on labour pain.DesignThe analgesic and sedative effects of intravenous morphine or pethidine and their effect on anxiety were compared in a prospective, double-blind, randomised dose-response study.SettingA Stockholm teaching hospital obstetric unit.ParticipantsTen healthy nulliparous parturients in active labour were included in each group.ResultsEven after repeated doses (up to 0.15 mg/kg body weight morphine and up to 1.5 mg/kg body weight pethidine) the findings were uniform, with very high pain scores maintained in each group as assessed with visual analogue scale. The parturients were all significantly sedated and several fell asleep but were awakened by pain during contractions.ConclusionIt is concluded that labour pain is not sensitive to systemically administered morphine or pethidine. These drugs only cause heavy sedation. It therefore seems unethical and medically incorrect to meet parturients' requests for pain relief by giving them sedation. Considering the well documented negative effects on newborn infants we also believe systemic pethidine should be avoided in labour.

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