Why these two are usually mentioned together, and why that is misleading

Both are drug-free, both are things you can start early, and both appear on every list of non-pharmacological options. But the guidance treats them very differently. NICE tells services to "offer the woman the opportunity to labour in water for pain relief" — an active recommendation. On TENS its language is much cooler, and it notes explicitly that "TENS devices are not provided by the NHS."

TENS: how it works

The NHS: "electrodes are taped on to your back and connected by wires to a small battery-powered stimulator. Holding this, you give yourself small, safe amounts of current through the electrodes. You can move around while you use TENS."

On mechanism, the NHS is appropriately hedged: "TENS is believed to work by stimulating the body to produce more of its own natural painkillers, called endorphins. It also reduces the number of pain signals sent to the brain by the spinal cord." The HSE describes the same endorphin mechanism.

The OAA adds that the current creates a tingling feeling and that "you can control the strength of the current yourself" — four flat pads stuck to your back, with no known harmful effects on your baby.

When it helps and when it stops helping

The NHS is unusually direct: "TENS has not been shown to be effective during the active phase of labour, when contractions get longer, stronger and more frequent. It's probably most effective during the early stages, when you may have lower back pain."

NICE says the same in guideline language: there is "very little evidence of its effectiveness in established labour, but no evidence of harm", and "other forms of pain relief can be used alongside TENS if needed by the woman."

The OAA is the most candid of the three: "while some people manage labour with only the help of TENS, it is common to need some other pain relief."

So the honest positioning is narrow but genuine: TENS is a tool for the latent phase and for backache, particularly at home, and particularly if you are planning a home birth. The NHS names exactly that use — "TENS may also be useful while you're at home in the early stages of labour or if you plan to give birth at home."

Practical points

Start early. The HSE: "using a TENS machine works better if you start early in labour."
Learn it before you need it. The NHS: "if you're interested in TENS, learn how to use it in the later months of your pregnancy. Ask your midwife to show you how it works."
Sort out where it comes from. The NHS notes some hospitals have machines and otherwise "you can hire your own machine". NICE confirms TENS devices are not NHS-provided. The HSE points to renting from large pharmacies.
Side effects. The NHS: "there are no known side effects of TENS for either you or the baby."

One incompatibility that is rarely mentioned: the electrodes are taped to your back, so TENS and a birth pool do not combine.

Water: what the guidance actually says

NICE's recommendation is an instruction to services, not a permission for you to seek: "offer the woman the opportunity to labour in water for pain relief."

The NHS explains the appeal without overclaiming: "being in water can help you relax and make the contractions seem less painful. Ask if you can have a bath or use a birth pool."

Note that this page is about labouring in water — using a bath or pool for pain relief during labour. Giving birth in the water is a separate decision with its own evidence and its own guidance.

The conditions attached

Water temperature. NICE: "the temperature of the water should not be above 37.5°C." The NHS repeats the same figure.
Monitoring. NICE requires that "for women labouring in water, monitor the temperature of the woman and the water hourly to ensure that the woman is comfortable and not becoming pyrexial."
Cleaning. NICE requires baths and birthing pools to be kept clean under a protocol agreed with local microbiology or infection control, and in line with the pool manufacturer's guidelines.
Opioids. NICE: "women should not enter water (a birthing pool or bath) within 2 hours of opioid administration or if they feel drowsy." This is the restriction most likely to catch you out, because it works in one direction — take the injection and the pool closes for two hours.

Access and mobility

NICE added a recommendation in 2025 that is worth quoting because it creates an entitlement: "support women and pregnant people with mobility issues to access water during labour and birth by doing an individualised needs assessment, and making reasonable adjustments for them based on this."

The practical obstacle is availability rather than policy. The OAA: "many maternity units have birthing pools, but these may not be available when you need them. Check with your midwife if there is a pool at your birth unit or hospital. Ask whether it is safe for you and your baby to use it."

The HSE lists a bath or shower among its self-help measures and notes that "some hospitals may have birthing pools" — the same hedge. If water is central to your plan, ask how many pools your unit has, not whether it has one.

Combining them with everything else

Neither of these closes any doors. NICE explicitly permits other forms of pain relief alongside TENS, and labouring in water does not prevent you asking for anything later — though moving to an epidural means leaving the pool, since NICE requires intravenous access and continuous monitoring for at least 30 minutes when regional analgesia is established.

The NHS lists both among the options that remain available at home, where an epidural is not: "epidurals are not available at home, but you can use gas and air, a warm bath, a birth pool, TENS and any relaxation techniques you've learned."

What we are not going to claim

No figure for how much pain either removes. Neither the NHS, NICE, the HSE nor the OAA publishes a percentage or a pain-score reduction for TENS or for labouring in water, and the guidance for TENS in established labour is expressly that the evidence is very thin. Any specific number you see attached to either is not coming from these sources.

TENS and Water for Pain Relief