Nitrous oxide alters pain perception. It can be used intermittently or continuously during labor. If you need to have a tear repaired after delivery, you might use nitrous oxide as a supplement to a local anesthetic. Self-administration might give you a sense of control over your pain management. If you become too drowsy, you'll be unable to continue holding the mask to your face and stop inhaling the anesthetic — a built-in safety mechanism. Nitrous oxide has little or no effect on the baby.