Introduction: This review of the safety and risks of nitrous oxide (N2O) labor analgesia presents results of a search for evidence of its effects on labor, the mother, the fetus, the neonate, breastfeeding, and maternal-infant bonding. Concerns about apoptotic damage to the brains of immature mammals exposed to high doses of N2O during late gestation, possible cardiovascular risks from hyperhomocysteinemia caused by N2O, a hypothesis that children exposed to N2O during birth are more likely to become addicted to amphetamine drugs as adults, and possible occupational risks for those who provide care to women using N2O/O2 labor analgesia are discussed in detail.
Methods: Research relevant to the 4 special concerns and to the effects of N2O analgesia on labor and the mother-child dyad were examined in depth. Three recent reviews of the biologic, toxicologic, anesthetic, analgesic, and anxiolytic effects of N2O; 3 reviews of the safety of 50% N2O/oxygen (O2) in providing analgesia in a variety of health care settings; and a 2002 systematic review of N2O/O2 labor analgesia were used.
Results: Nitrous oxide analgesia is safe for mothers, neonates, and those who care for women during childbirth if the N2O is delivered as a 50% blend with O2, is self-administered, and good occupational hygiene is practiced. Because of the strong correlation between dose and harm from exposure to N2O, concerns based on effects of long exposure to high anesthetic-level doses of N2O have only tenuous, hypothetical pertinence to the safety of N2O/O2 labor analgesia.
Discussion: Nitrous oxide labor analgesia is safe for the mother, fetus, and neonate and can be made safe for caregivers. It is simple to administer, does not interfere with the release and function of endogenous oxytocin, and has no adverse effects on the normal physiology and progress of labor.