Gas and air is a mix of 50% nitrous oxide and 50% oxygen that you breathe through a mouthpiece or mask during contractions. It’s one of the most widely used forms of pain relief in labor, especially in the UK, and it works by triggering your body’s own natural painkillers. The effect kicks in within seconds and wears off just as fast once you stop breathing it in.
What’s in It and How It Works
The gas is delivered from a single cylinder (often sold under the brand name Entonox) containing a precise 50/50 blend of nitrous oxide and oxygen. You hold a mouthpiece or mask and breathe in deeply when a contraction begins. The nitrous oxide crosses from your lungs into your bloodstream almost immediately, reaching full effect within one to two minutes.
Once in your system, nitrous oxide stimulates the release of your body’s own opioid-like chemicals called dynorphins. These natural compounds activate pain-suppressing pathways in your brain and spinal cord, dulling the intensity of contractions without blocking sensation entirely. The mechanism is similar in nature to how morphine works, but because you’re producing the chemicals yourself and the gas clears quickly, the effect is much milder and shorter-lived. When you stop inhaling, the gas leaves your blood through your lungs within seconds.
How to Use It During Contractions
Timing matters. Because the gas takes roughly 30 to 50 seconds to reach peak levels in your blood, you should start breathing it in just before a contraction begins, not during the peak. If you wait until the pain is already intense, the gas won’t have time to build up before the contraction fades. Most people learn the rhythm after a few contractions.
You control the flow yourself. The system uses a demand valve, meaning gas only releases when you actively inhale through the mouthpiece. If the gas makes you drowsy or lightheaded, you’ll naturally stop gripping the mouthpiece or slow your breathing, which acts as a built-in safety limit. No one else administers it for you, so you’re always in charge of how much you take in.
How Well It Relieves Pain
Gas and air takes the edge off contractions rather than eliminating pain completely. In one large study, women rated their satisfaction with nitrous oxide at 7.4 out of 10. That said, about 69% of women who started with gas and air eventually switched to another method, and 92% of those chose an epidural. This doesn’t mean the gas failed. Many women find it useful in early labor or as a bridge while waiting for an epidural to be placed, and others appreciate simply having the option.
Unlike an epidural, gas and air lets you keep full strength and freedom of movement. You can walk, change positions, use a birthing ball, or get into a pool. There’s no needle, no catheter, and no waiting for an anesthesiologist. That flexibility is a significant reason many women prefer it, at least for part of their labor.
Side Effects
Most women experience some level of side effects, though they tend to be mild. In one study, about 94% of users reported at least one side effect, but 63% described the discomfort as slight. The most commonly reported effects include dry mouth (around 70% of users), drowsiness (roughly 35%), dizziness (25%), headache (25%), and nausea (about 10%). These side effects disappear quickly once you stop breathing the gas, usually within a few breaths of normal air.
Some women also feel briefly euphoric or disconnected, which is why nitrous oxide is sometimes called “laughing gas.” This feeling fades just as rapidly. If any side effect bothers you, you simply put the mouthpiece down and wait a few seconds.
Safety for the Baby
Research consistently shows no measurable impact on the baby. In a study comparing 200 women using gas and air with 200 breathing only oxygen, newborn health scores (Apgar scores) were virtually identical at both one minute and five minutes after birth. There was no significant difference in the baby’s oxygen levels or heart rate patterns during labor. The gas crosses the placenta, but because it clears from the bloodstream so quickly through breathing, it doesn’t accumulate in the baby’s system.
Who Should Avoid It
Gas and air is safe for most laboring women, but certain conditions rule it out. You shouldn’t use it if you have a collapsed lung (pneumothorax), a bowel obstruction, or any condition involving trapped air pockets in the body, because nitrous oxide can cause those pockets to expand. It’s also contraindicated after certain eye surgeries that use an internal gas bubble.
If you have a known vitamin B12 or folate deficiency, your care team will weigh the decision carefully, since nitrous oxide can interfere with how your body uses these nutrients. The same caution applies if you have a history of stroke, low blood pressure, or significant heart conditions. For the vast majority of women in labor, though, the gas poses no special risks.
How It Compares to an Epidural
The two options serve different roles. An epidural blocks pain signals from the lower body almost entirely, making it far more effective at eliminating contraction pain. Gas and air reduces pain perception without removing it. The tradeoff is that an epidural requires an anesthesiologist, a needle in the lower back, continuous monitoring, and typically limits your ability to walk or change positions freely. Gas and air requires nothing more than picking up a mouthpiece.
Many birth plans combine both. Gas and air can be started the moment contractions become uncomfortable, with no setup time and no commitment. If you later decide you want stronger relief, switching to an epidural is straightforward. Using gas and air first doesn’t limit your options in any way, and some women continue using it even after an epidural for additional comfort during particularly intense moments of pushing.
Availability Around the World
Gas and air has been a standard option in maternity units across the UK, Australia, Canada, and much of Europe for decades. In the United States, it’s less common but has been growing in availability since around 2011, when hospitals and birth centers began reintroducing it. One reason for slower adoption in the US relates to ventilation requirements: healthcare facilities must manage staff exposure to nitrous oxide that escapes into the room. The UK’s Health and Safety Executive sets a workplace exposure limit of 100 parts per million over an eight-hour shift, and maternity units use scavenging systems attached to the mouthpiece or mask to capture exhaled gas before it enters the room air. Hospitals that invest in this equipment can offer the option safely for both patients and staff.