Nitrous oxide (N2O), also known as laughing gas, has been used for pain relief during dental procedures since mid-19th century. In the 20th century, its use also became common in childbirth, but lost popularity in the USA with the development of other pain control options.
The gas is still commonly used as labor analgesic in Canada and many European countries, and it is slowly returning to US hospitals as more and more women seek to control labor pain in a less invasive way than epidural anesthesia.
The U.S. Food and Drug Administration approved new nitrous oxide equipment for childbirth use in 2011, which may also explain its revival.
Nitrous oxide used for labor pain is a mixture of 50 percent nitrous gas and 50 percent oxygen, which women self-administer (inhale) through a mask or mouthpiece. While the pain may still exist for some women, the gas should decrease the intensity.
In addition to the gas being a less invasive option, it also offers significant cost savings to women. The average cost for nitrous oxide is roughly only 3-5 percent of the cost of an epidural anesthesia fees.