Click here for the full review, published in the Canadian Journal of Anesthesia.
Here is one paragraph of interest:
All opioids have the potential to decrease baseline FHR and reduce variability, making interpretation of fetal CTG recordings potentially problematic. It has been documented from observational studies that parenteral narcotics can be associated with neonatal respiratory depression, decreased neonatal alertness, inhibition of sucking, and a delay in effective feeding. When evidence related to the use of parenteral opioids for labour pain relief was subject to a systematic review,54 it was noted that none of the studies was sufficiently powered to address the primary outcome measure of neonatal resuscitation, a measure of safety. Intramuscular opioid was compared to placebo, different im [intra-muscular] opioid, same im opioid but different dose, and same opioid given intravenously. Intravenous opioid was compared to different iv opioid and same iv opioid but different modes of administration. There was insufficient pooled information to draw conclusions regarding any of the secondary outcome measures, including fetal distress, administration of naloxone, Apgar score < 7 at five minutes, neonatal mortality, admission to a special care setting, feeding problems, and problems with mother-baby interaction.