I will not sugarcoat it: labor without pain medication really, really hurts. This doesn’t necessarily mean you don’t want to have an un-medicated birth (I did; more on this in Expecting Better), but it does explain why pain relief during labor has been a subject of intense interest over the years.

In the US the most common approach to pain relief during labor is the epidural. This is because an epidural is really, really effective pain relief for most women. But it’s not the only option! For decades, women outside the US (mostly in Europe) have used other forms of pain relief, and one of the more popular is nitrous oxide; in the UK this is often called “gas and air”. If you are a fan of “Call the Midwife” (which you should be) you’ll see them using it there.

And now, increasingly, this is becoming available in the US. So: what is it, does it work, is it safe? Evidence review, here we come.

What is nitrous?

Basically, it’s a mix of nitrous oxide and oxygen (usually a 50/50 combo) which is inhaled through a mask at the start of a contraction (or, ideally, shortly before it starts). The laboring woman holds the mask over her own mouth, and breathes in. The gas provides temporary pain relief. You take the mask off as the contraction ends. You can choose to use it or not for each contraction.

Does using nitrous make labor less painful?

We do not have amazing data on this. There are a few small randomized trials (by small, think a few hundred people). A 2012 Cochrane Review provides a nice summary. Relying on these small samples, the answer seems to be that, yes, it can provide some pain relief. Women in the nitrous group were much, much less likely to rate their pain as severe/extreme (like 95% less likely) than those in the placebo group.

However, the pain relief from this is temporary and intermittent. You probably want to think of it more like “taking the edge off” than “making me feel awesome”. If you are looking for fuller pain relief, it’s pretty clear the epidural is the way to go. The Cochrane review describes it as “not remotely similar” to the epidural in this dimension.

Consistent with this last point, in at least one case when a hospital introduced this option it did not change the share of women who had an epidural. In other words, in that case it didn’t seem like women who would otherwise have had the epidural opted for the nitrous.

Is using nitrous during labor safe?

Yes. At least for the laboring woman and baby. The short-term nature of the treatment means it is cleared from the system quickly, and the fact that the woman controls the mask herself limits the risk of inhaling too much (basically, you’ll get drowsy and drop the mask if you overdo it). Randomized trials show no excess risk of bad outcomes for infants, and no changes in APGAR scores.

Nitrous also doesn’t seem to affect the progress of labor. There’s no evidence of an increased risk of C-section or need for forceps or a vacuum delivery as a result. These are risks which do come up in the context of the epidural.

The one group who may be affected are hospital workers; continual exposure to nitrous oxide isn’t thought to be healthy. This is an issue for hospitals to contend with, and probably not a major part of the decision for most pregnatn women.

Are there downsides to nitrous?

Also, yes. Nitrous can make you nauseous, cause you to vomit and make you dizzy and tired. Indeed, in randomized trials these outcomes are very, very elevated. Relative to women who use no pain relief, those with nitrous are 43 times as likely to be nauseous, 9 times as likely to vomit and 113 times as likely to report dizziness. These are consistent with our basic understanding of non-pregnant reactions to this gas, so this isn’t surprising.

Okay, so should I use it?

Hm, I think it depends. If you are seeing this as an alternative to an epidural, that’s probably not the right way to think about it. Where I think this may be a good option is for women who would like to labor without an epidural, but are looking for some temporary relief during the most intense periods. An advantage of the nitrous is you can decide to use or not use it at any time. Some contractions on, some off, etc. It is also possible to use it while, say, in a birthing tub (indeed, when I looked for pictures of this they were almost all of women in birthing tubs).

If this had been available to me I bet I would have used it, at least with my first birth. It might have limited the amount of time I spent clawing at my face during the last part of labor.