Most expectant moms want some form of pain relief during labor. However, some are really concerned about the lack of control and ability to move that comes with an epidural. This is a valid concern. Before epidurals, nitrous was used in the US and is still used in the UK, Australia, and Canada.
So how does nitrous oxide work? Nitrous oxide is a clear colorless gas. It enters the blood by diffusion and is not metabolized by the body. It is then eliminated by diffusion out of the lungs and therefore has its effect for roughly two minutes for on and offset. This means when you inhale it, you will only feel the effects for about two minutes! Nitrous oxide provides some pain relief but is mostly an anxiolytic (helps relieve anxiety). It makes people feel euphoric and relaxed (You want to drill on my teeth, go for it, because I don’t care!). This happy feeling is why it is called “laughing gas”. It is usually administered with oxygen because there is a risk of death from lack of oxygen when used alone. Side effects of nitrous include nausea, vomiting, headache, increased sleepiness and/or excessive sweating or shivering.
So, what are the advantages of using nitrous to help control labor pain? As the patient, you have a lot of control over when to use it (mask on, mask off). It’s a lot cheaper than an epidural because it does not require the expertise of an anesthesiologist or a nurse anesthetist. Anyone can show you how to breathe through the mask. This may be why it is used so routinely in countries with socialized medicine. It has a rapid onset of action and is easily reversible. Lastly, (and possibly most importantly) it might make your doctor's jokes funny :)
So, what are the disadvantages of using nitrous to help control labor pain?
First of all, the effects of nitrous only last 2 minutes! Can you imagine being in labor for 20 + hours and having to replace that mask every 2 minutes. In addition, your caretakers would continuously be worried about your oxygen saturation.
Second, nitrous readily crosses the placenta and can have anesthetic effects on the fetus. One of the main reasons so few labor and delivery wards offer nitrous as an option is because they need to have special equipment that can mix nitrous and oxygen. The percent of nitrous you would receive at a dentist’s office is much higher than the nitrous you would receive in labor, hence it would be less effective. If you received the same amount of nitrous in labor as you did in the dentist office this could easily cause hypoxia (oxygen level is too low for safety) in mom. This could then easily cause fetal and newborn hypoxia, which is one of the most common causes of operative vaginal delivery or cesarean section.
Nitrous is more sedating than an epidural. It can also cause altered consciousness and impaired memory. So, while you can move while inhaling nitrous, that may not be the safest option (kind of like we wouldn’t suggest driving drunk as it could cause a crash, walking while receiving nitrous gas could also lead to a crash for mom and baby). That being said, it may make for some pretty incredible (and YouTube ready) labor and delivery videos!
Lastly, there are no great studies that look into the safety and efficacy of nitrous. Most of the studies were not performed in the US, and of the ones that were, they did not include enough women or use standardized methods to provide reliable results. One day nitrous may be a good option for pain control in labor. However, first we need some better studies, especially ones that look into long term effects on the fetus, before offering it as a safe option for pain control.