Dose-Delivery Time Interval of Morphine in Labour and its Impact on the Likelihood of Adverse Neonatal Outcomes

Background: To find the effect that time between dosage of morphine and delivery of the baby has on the incidence of need for neonatal resuscitation. Methods: Retrospective analysis of 659 births at The Northern Hospital, Epping, Victoria, featuring use of morphine in labour. Time between morphine dose and delivery of baby was recorded for each birth, known as the dose-delivery interval (DDI). Four equally distributed categories were created based on quartiles of DDI. Various neonatal outcomes were compared between the groups, including need for resuscitation, and type of resuscitation used. Univariate and multivariate analysis were performed using IBM SPSS version 26. Results: Dose-delivery category 2 (155-314 minutes) was found to have significantly higher odds of requiring neonatal resuscitation (OR 2.08; 95% CI 1.20-3.59 P = 0.009), in addition to specific forms of resuscitation such as tactile stimulation (OR 2.05; 95% CI 1.20-3.51 P = 0.009), continuous positive airway pressure (OR 2.51; 95% CI 1.205.25 P = 0.015) and intermittent positive pressure ventilation (OR 6.67; 95% CI 2.53-17.62 P < 0.001) compared to the longest dose-delivery category (> 526.5 minutes). Subcutaneous morphine was also found to have lower odds of neonatal resuscitation (OR 0.22; 95% CI 0.068-0.69 P = 0.009) and specifically tactile stimulation (OR 0.24; 95% CI 0.08-0.77 P = 0.016) compared to intramuscular morphine. Conclusion: A dose-delivery interval between 155 and 314 minutes may lead to a higher incidence of requirement for resuscitation at birth, in addition to specific types of resuscitation including tactile stimulation, continuous positive airway pressure and intermittent positive pressure ventilation.