Nitrous oxide analgesia: a "middle path" between highly medicalized and completely natural childbirth

Dr. Copeland By Dr. Copeland, 4th Jan 2011 | Follow this author | RSS Feed
Posted in Wikinut>Family>Pregnancy

Nitrous oxide analgesia during labor is a mild alternative to the extremes of epidural anaesthesia and completely unmedicated birth.

Labor pain, analgesia, and natural birth

As a mother who has given birth naturally (no drugs or major interventions), I know firsthand how difficult the natural birth process can be. Though non-invasive techniques like hypnobirthing and acupressure worked wonders to ease the pain of my labor, it was still the most intense pain I have ever experienced. I have lost count of the number of friends who ardently wanted a natural birth, but then caved in when the pain became too extreme. I have often thought that what so many women could use is a "middle path"; a mild analgesic that could be safely used during birth, with little or no effects on the baby being born. It would be OK if this analgesic let in some pain; for me, and for many women attempting natural birth, it would make all the difference to have just "a little something to take the edge off".

Nitrous oxide: a mild alternative

As it so happens, that "little something" is available to women in almost every developed country—except the United States. The drug is nitrous oxide, or laughing gas. It is mild, has little or no effects on the baby being born, and is used by midwives throughout the world for labor. It is not a strong anaesthetic, but it is effective for many women. Dr. Mark Rosen, M.D., of UCSF Moffitt Hospital in San Francisco, describes it this way: "Although the efficacy of nitrous oxide has not been well defined and seems limited compared with that of epidural analgesia, it appears to provide analgesia at a level comparable to that of paracervical block and probably better than that provided by opioids. When applied properly, it appears that nitrous oxide inhalation can provide significant pain relief for at least 50% of patients, a conclusion reached 30 years ago." In the U.S., however, it is currently available only in San Francisco (UCSF Moffitt Hospital) and Seattle (University of Washington Hospital), with approval for future use in one small community hospital in Hawaii (North Hawaii Community Hospital). For the overwhelming majority of women giving birth in the United States, nitrous oxide is not available as a choice.

Benefits of nitrous oxide

Why is this mild alternative pain reliever not more widely available to American laboring mothers? Babies born under nitrous oxide analgesia are not significantly affected by it; Apgar scores, neonatal survival, and neurobehavioral assessments (Neurologic and Adaptive Capacity Score and Early Neonatal and Behavioral Scale) are not significantly different from those for unmedicated birth. Also, it is excreted through the lungs, so in less than a minute, it is eliminated from the baby's body. (In contrast, the opiates and cocaine-derivatives used in epidurals are processed through the liver. A newborn baby's immature liver can take months to eliminate the drugs.)

Mothers like nitrous oxide because, in contrast to the epidural, it does not lead to the "chain of interventions" that often ends in cesarean section, which has become the birth method for almost one in every three American mothers. Nitrous oxide also has no significant effects on the natural progress of labor. When used under standard conditions, side effects are minimal (such as dizziness or euphoria), and there is no significant difference in maternal oxygen saturation compared with completely unmedicated births and births with an epidural. (Standard conditions for use of nitrous oxide during labor include a 50% oxygen mixture, scavenging equipment and a one-way valve to minimize escaping gas, and a hand-held mask, so that, if a woman were able to ingest a dose high enough to make her very dizzy or faint, her hand would fall from her mouth and the flow of gas would stop.) Judith Rooks, a midwife and advocate for the use of nitrous oxide, states that "it is particularly helpful for women experiencing rapid labor, transition, second-stage labor, and while suturing the perineum. It can be extremely helpful for women who want to avoid an epidural, useful for women who have to wait for an epidural, and a blessing for everyone when there is a sudden, unexpected need for analgesia for an invasive procedure required because of an obstetric emergency."

Concerns about nitrous oxide

So, again, why is this option not more available to American laboring women? One legitimate concern is the occupational exposure of midwives and other workers to nitrous oxide. Midwives exposed to nitrous oxide (continuously, over 7.5- to 11-hour shifts) in older, unventilated hospitals in the U.K. had chronic exposures in excess of U.S. OSHA limits. (U.S. OSHA guidelines are more stringent than those of most other countries.) This could lead to reduced fertility in female workers. However, midwives in newer hospitals with modern ventilation were found to have levels well below U.S. OSHA limits, even when the hospitals did not use scavenging equipment. Other studies of hospitals/birth centers/dental clinics have shown low levels of exposure when scavenging equipment is used. According to Dr. Rosen, the key is to use scavenging equipment; even if nitrous oxide is relatively safe, why not just get rid of it, so workers do not have to worry about occupational exposure? Scavenging equipment is a standard part of modern nitrous oxide equipment for laboring women.

Another concern that has been expressed is that of apoptosis, the type of natural cell death that protects us from cancer, but can be a problem when taking place unnaturally. Unlike the real-world issue of occupational exposure to nitrous oxide, this effect has only been seen in laboratory animal studies at doses approximately 50 times that a laboring woman would ingest, a dose women in labor would never receive. (In fact, hyperbaric chambers had to be used to deliver the continuous, six-hour superatmospheric doses used in these experiments, since it is impossible to achieve a dose this high at normal atmospheric pressure.) Since many/most drugs in use have much more serious effects (e.g., death) at far lower than 50X effective-doses, this actually reflects the safety of nitrous oxide, especially compared with other analgesics.

Effectiveness of nitrous oxide

Many feel that the reason for nitrous oxide's lack of availability here is that it is only a mild-to-moderately effective form of analgesia, in contrast to the very strong effects of an epidural. Judith Bishop, a midwife who works with nitrous oxide at the UCSF Moffitt hospital in San Francisco, states that "Not all laboring women who try it find it useful. Those who do either report reduced pain or acknowledge they are still in pain but care less about it." There is a prevalent idea that women do not want a mild form of pain relief that is only somewhat, rather than 100%, effective, but this presupposes that all women want 100% pain relief, unless they want to be 100% drug-free, and does not acknowledge the true diversity of women and their birth wishes.

Laboring women are often grouped together as one homogenous bloc, but in fact, the birth wishes of pregnant women are as diverse as the women themselves. With respect to pain relief, many women do want complete anaesthesia. "Knock me out- I don't want to feel anything!" is a common refrain for many pregnant mothers-to-be. For these women, the highly medicalized birth options available in the U.S. are perfect- complete anaesthesia through an epidural can enable an easy birth, and many mothers have been quite happy with this option. At the other end of the spectrum are women who want a completely unmedicated birth, with no drugs of any kind. This option is becoming increasingly available, through alternative birthing centers, home-birth midwives, and more progressive, patient-centered hospitals. Many health professionals believe that all women are at either one or the other end of this spectrum. However, there are other women who want to have a birth that is as natural as possible, but also would like "just a little" pain relief to help them achieve their goal. This is the strength of nitrous oxide. As midwife Judith Rooks states, "N2O is not right for every woman during labor, but it is wonderful for some women."

Further reading

Nitrous oxide for relief of labor pain: a systematic review.
by Rosen MA. Am J Obstet Gynecol. 2002 May;186(5 Suppl Nature):S110-26.

Administration of nitrous oxide in labor: expanding the options for women.
by Bishop JT. J Midwifery Womens Health. 2007 May-Jun;52(3):308-9.

Use of nitrous oxide in midwifery practice--complementary, synergistic, and needed in the United States.
by Rooks JP. J Midwifery Womens Health. 2007 May-Jun;52(3):186-9.


Alternative Analgesia, Baby, Birth Pain, Childbirth, Delivery, Drug-Free Birth, Entonox, Epidural, Labor, Labor Anaesthesia, Labor Pain, Labour, Labour Pain, Laughing Gas, N2O, Natural Birth, Nitronox, Nitrous Oxide, Nitrous Oxide Analgesia

Meet the author

author avatar Dr. Copeland
Dr. Copeland holds a Ph.D. in molecular and cellular biology from Tulane University, specializing in tropical medicine, parasite genetics, and retrotransposons/retroviruses, with postdoctoral research experience in molecular entomology and computatio...(more)

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author avatar L. Garcia
7th Nov 2016 (#)

For up to 15% of the population, use of nitrous oxide increases the risk of stroke or death due to rapid rise in homocysteine. Mothers and babies would first have to be genotyped to eliminate the risk of death or injury to the mother or child. Published scientific literature is available documenting this risk in people who are homozygous for MTHFR variants that impair the enzyme. The following information, however, seems especially helpful as it describes the potential manner of death of the infant exposed to nitrous oxide

Savage S., Ma D. The neurotoxicity of nitrous oxide: The facts and “putative” mechanisms. Brain Sci.2014;4:73–90. doi: 10.3390/brainsci4010073.
"One striking example of this is a case report involving a young child (3 months old) with an MTHFR gene mutation, leading to an MTHFR enzyme deficiency . This particular patient was administered 60% N2O on two occasions during surgery, and within 3 weeks after surgery was admitted to hospital suffering from seizures. Less than 2 months post-surgery the patient had died and was found to have severe lesions in the brain, as well as nerve demyelination. At such a young age it is probable that the brain was extremely sensitive to molecular changes and the rapid and extreme increase in homocysteine levels appears to have been involved in the patient’s death. This again highlights the need for clinicians to be vigilant in ensuring their patients are not at risk if exposed to N2O. It also showcases the range of physiological parameters which are important to be aware of before administering N2O, which dentists and paramedics, who routinely use N2O as an analgesic and anxiolytic, do not normally have access to."

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