Umbilical cord plasma concentrations of free morphine following single-dose diamorphine analgesia and their relationship to dose-delivery time interval, Apgar scores and neonatal respiration.

Objective: To find the effect of dose-delivery interval on cord-blood levels of diamorphine metabolites and its effect on Apgar sores and neonatal respiration.

Study Design: Pilot study conducted in labour ward of a district general hospital. One hundred women who had normal delivery and received single dose of 7.5mg of intramuscular injection of diamorphine in labour were recruited in the study. A 2.0 ml sample of umbilical venous blood was collected from the placenta after delivery of the baby. The sample was analysed using RIA method to measure free morphine. Details about the labour and baby's condition at birth were recorded.

Results: The concentration of free morphine in the umbilical venous blood was significantly associated with the dose-delivery interval (coefficient (95% CI)=1.08(0.99-1.18), p<0.001). Twenty neonates had low Apgar score (< or =7) at 1 min. The odds of such a low score were raised with higher log free morphine in the cord venous plasma, but not statistically significantly (OR (95% CI)=5.3 (0.84-34), p=0.08). Fourteen neonates required resuscitation. The odds of requiring resuscitation were significantly raised with higher log free morphine: OR (95% CI)=9.3 (1.0-86), p=0.05.

Conclusion: Concentration of free morphine in the umbilical venous blood after delivery was significantly associated with the dose-delivery interval and this had significant effect on the need for resuscitation.