Patients who are pregnant or may be pregnant should tell their dentist about their condition. Conclusive evidence concerning the safety of nitrous oxide in pregnant or breastfeeding women is not available.

Nitrous oxide may be recommended for pregnant women or breastfeeding mothers who need dental treatment because it works quickly, wears off quickly and is not metabolized (broken down and absorbed) in the body. It is a mild sedative and one of the least harmful types of anesthesia.

However, indirect evidence indicates that pregnant women who receive nitrous oxide over longer periods of time have a higher rate of miscarriage or spontaneous abortion than women not exposed to the gas. Some animal studies indicate anesthetics that are inhaled, such as nitrous oxide, can cause birth defects in an unborn fetus. This risk is higher for healthcare providers working in an environment of prolonged exposure to nitrous oxide (e.g., a dental office) than in patients who are only briefly exposed to the gas. Also, women exposed to the gas for more than five hours per week were found to be less fertile than women not exposed to the gas.

Women who are pregnant, breastfeeding, or planning to become pregnant, are encouraged to speak to their dentist about concerns they may have regarding the use of nitrous oxide.