Sterile Water Injections for Labour Pain Relief: Everything You Need to Know

Sterile water injections can provide a few hours of relief for those experiencing back pain in labour.

Pain is part of the labour process, but there are many options for pain management. Everybody has different pain tolerances and different desires for their birth so it is entirely your decision whether you would like to have any medical pain relief or not. Here, we discuss sterile water injections for labour in New Zealand.


What are sterile water injections?

For those experiencing persistent back pain during labour (usually caused by baby being in a posterior position), four injections of sterile water are administered in four locations in the lower back, into the dermal layer of the skin. The injections cause a strong bee or wasp-like sting when given.


How do sterile water injections work?

Researchers believe they work by initiating what’s called the ‘diffuse noxious inhibitory control’ method. Essentially meaning that by stimulating pain in the lower back with the administration of the injections, the brain releases its own pain-lowering hormones called endorphins, so the person in labour perceives their pain to be lessened.

When administered, the onset of pain relief is relatively instantaneous; the stinging sensation lasts around 30 seconds and as that feeling dissipates the pain relief element also takes effect. The effects can last up to three hours.


Side effects

  • The only side effect is the transitory pain experienced immediately after the injection is given.



  • An effective method for relieving lower back pain in labour – 90% of people experience less pain after the injections compared to before.
  • Can be given any time during labour.
  • No side effects the baby.
  • In one systematic review, researchers found that when sterile water injections were used for low back pain, compared to placebo or alternative therapy (including acupuncture and TENS), the rate of caesarean section decreased. The caesarean section rate was 4.6% in the sterile water injection group and 9.9% in the comparison group.



  • The strong stinging sensation that is caused when the injections are administered, however this is essential to achieve an analgesic (pain relieving) effect.
  • Small risk of site infection, as with any other injection.



At home, in a birthing unit, or hospital. However, not all midwives are trained in the technique and many do not practise it regularly.

If you’re open to using sterile water injections during your labour, it’s a good idea to ask your LMC if they practise the technique when you discuss your birth preferences.