Nitrous Oxide (N20) is otherwise known as laughing gas. It is an anaesthetic gas that has been used since the beginning of the last century. It is commonly used during surgery and as a pain relief method during labour. A lot of people will have come in contact with Nitrous Oxide at their dentist. Nitrous Oxide is mixed with oxygen. The concentration of Nitrous Oxide that a woman in labour receives varies between 30 to 70%. Nitrous Oxide is breathed into the lungs and there it very quickly enters the blood stream. Nitrous Oxide reaches the brain within 15 seconds. The amount of Nitrous Oxide that reaches the brain varies, depending on the strength administered and how long it has been used. The normal function of the brain is depressed to varying degrees. However the way Nitrous Oxide provides pain relief is unknown.
The effectiveness of Nitrous Oxide as pain relief in labour varies from woman to woman. Less than 50 per cent of women find it a satisfactory form of pain relief, 20 per cent obtain some pain relief for some of the time and around 30 per cent find it totally ineffective. There have been reports regarding the declining use of Nitrous Oxide as a pain relief in labour in recent years, due to its inability to provide a reliable form of pain relief.
Nitrous Oxide and oxygen can be given from either a fixed or portable apparatus. The fixed apparatus is attached to the wall and varying concentrations of Nitrous Oxide and oxygen can be given. The midwife adjusts the dosage to what is required. However as it cannot be moved, a woman in labour cannot use Nitrous Oxide in the shower, bath or at a homebirth. Nitrous Oxide and oxygen can also be given from a portable cylinder. The dosage is fixed (a 50:50 mixture of Nitrous Oxide and oxygen is in the cylinder - this known as Entonox). With Entonox it is not possible to alter the concentration of Nitrous Oxide that a woman receives.
Nitrous Oxide is breathed in by the woman either using a face mask or mouth piece. To use it correctly the woman begins breathing on the mouth piece or face mask deeply at the beginning of a contraction until a rattling sound is heard. The Nitrous Oxide and oxygen mixture is then breathed in throughout the whole contraction and is stopped as soon as the contraction is over. Nitrous Oxide can be given at any time during labour, but is most likely administered during transition.
Once Nitrous Oxide enters the blood stream, it is very quickly distributed around the body. It passes just as quickly across the placenta and into the baby’s circulation. Nitrous Oxide (unlike drugs like pethidine) is not broken down by the liver and therefore does not leave by-products. Nitrous Oxide is able to be eliminated quickly from the woman’s body entirely by her lungs. Nitrous Oxide is also eliminated quickly from the baby’s body. When using Nitrous Oxide it is important to start using it as soon as the contraction starts due to the 15 seconds it takes to become effective. Once the woman stops breathing the Nitrous Oxide and oxygen mixture and begins to breath air again, the effects of the Nitrous Oxide wears off quickly.
The advantages of using Nitrous Oxide during labour is that it provides some pain relief for some women. Women using Nitrous Oxide remain awake and in control of their own pain relief. Nitrous Oxide does not interfere with contractions, the time Nitrous Oxide remains effective is short and there are no obvious short term effects on mother and baby that have been noted to date.
Disadvantages of using Nitrous Oxide during labour include:
Whether there are any long term effects of Nitrous Oxide on babies is difficult to answer. I could find only one study on this question. In a well designed case control study conducted in Stockholm by Jacobson et al. (1990) they found that when Nitrous Oxide was given to a woman during labour, that child (in later life) was five and a half times more likely to have an amphetamine addiction than a brother or sister who did not receive Nitrous Oxide via their mother during labour.
(25th September 2000)
8 comment(s) on this page. Add your own comment below.
It will no doubt come as a shock to many well meaning anesthesiologists and nurses who do not have access to current information on this topic. It is painful to realize that US medical schools do not teach accurate information and to worry that information is being withheld or altered in order to promote the staus quo or to fulfill profit motives.
It is important that balanced information is provided so people can make informed decisions regarding their health care.
Dear Jane, This is the first pregnancy article I've come across where the author has actually provided a balanced argument and, importantly, references! Thank you!
These three references are very dated. Has the 1990 study ever been replicated? Considering that probably half of all women birthing in hospital try entonox at some point in their labours, it doesn't seem that half the adult population are drug addicts.
I think you need to assess the evidence more carefully before you post these comments on the internet. I disagree with Ci-Sun. As a health professional, we are educated enough to weigh up the evidence and see that three very old papers (not current information at all) are not enough to change recommendations for offering pain relief to women in labour.
Dear Kelly - Nitrous Oxide use in labour has not been researched well. Point taken the article needs updating (I wrote it in 1999). However just because the research is old - does not mean it is not relevant. To my knowledge no one has repeated the Jacobson et al studies (they did several on different drugs in labour). Further research is necessary. There has not been any long term studies on the use of nitrous oxide - so we don't know if there are any effects long term from using Nitrous Oxide in labour.
I just did a search on the Cochrane Database to see what it said on Nitrous Oxide use - see this link. This review is old 2002 and is of questionable quality.
I must say I was a little bemused by your comment "Considering that probably half of all women birthing in hospital try entonox at some point in their labours, it doesn't seem that half the adult population are drug addicts" - no where in the article does it suggest that. It does say that the Jacobson study showed an increased incidence of drug addiction when they compared siblings nothing more.
I am very interested in using this for my childbirth, we are in our 3rd month of trying, I am actively looking for information regarding midwives that use this technique. Any chance you have any contacts I could talk to.
Your dentist is wrong and clearly does not understand the physiology of labor. The Nitrous Oxide has no interaction with the oxytocin cascade that effects the strength and spacing of uterine contractions. If anything, its anxiolytic effects might improve labor efficiency. Next time - don't ask your dentist to weigh in on maternal health.