Sterile Water Injections

Sterile water injections are used for back pain in labour and involve injecting 4 x small amounts (0.1 – 0.5ml) of sterile water just under the skin. The effect is almost immediate and as it is not a drug, has no effect on the baby.

Sterile water injections work on the pain ‘gate control theory’. The skin has thousands of receptor sites and nerve cell endings for pain, pressure, touch etc., and transmits that information to the brain very, very quickly. The sensations shoot up the nerves and spinal cord to the brain. The sensations (which are chemical and electrical signals) go through neural synapses (nerve gates). The signal boxes in the nerve pathways are ‘manned’ by chemical signallers which let pain, pressure, touch etc., signals through to the brain. They are called gates because they choose which signal to let through. When the brain receives the signals, it decides what action to take. When a woman has back pain in labour, the pain signals are slow signals. Some back pain is normal when the baby’s head is descending in the pelvis however, when a woman has unbearable back pain in labour the water injections may be useful.

Water injections are given intradermally (just under the skin) in the lower part of her back (around the site of the backpain) It stings intensely for about thirty seconds. This is important as the sting switches on the fast fibres. The fast fibre signals from the skin come racing up to the gate, close the gate to the slow pain messages and let the quick skin related message through. The internal pain signal is stopped in its tracks and the woman no longer feels that internal sensation.

That effect lasts from about 30 minutes to 2 ½ hours.  Sterile water injections are very effective for the majority of women. To get maximum benefit, the intensity of the back pain has to be considered strong enough so that the wasp-like sting felt with the water injections is worth it.

If the woman’s backache is 7-8 out of 10 (0 = no pain, 10 = worst pain) she would be a good candidate for water injections. It should work by the next contraction and take away the back pain. Most women are then able to cope with the contractions without the constant back pain.

Sterile water injections work for over 85% of women with back pain in labour. They are quick, easy and safe.

Water injections may be repeated if required but mostly the relief of the internal pain enables the woman to relax. This will help the pelvic muscles relax, the baby to rotate into position and the cervix to dilate.  A woman can choose other pain relief options if she desires after having sterile water injections.

 

 

 

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