Approximately 30% of women experience severe back pain in labor, particularly those with posterior births. Unlike uterine contractions, the back pain is constant, and the distress from the back pain makes it difficult to rest and remain calm between contractions.

In recent years labor wards have been offering women subcutaneous injections of sterile water into 4 points in the lumbosacral region to reduce their pain. The injection itself is very painful, like an intense wasp sting, but lasts less than 30 seconds. It is usually administered quickly during a contraction by two midwives at the same time to make it more bearable.
sterile water injections

HOW DOES IT WORK?

The body automatically reacts to skin pain before internal pain, because it recognises skin pain as being potentially more threatening. The injections serve as “counter-irritation”, and trick the brain to remain alert for further skin pain, and pay less attention to messages of back pain. Effectively it causes a short-term change in the messages in the nervous system.

HOW EFFECTIVE IS IT?

A recent randomised controlled trial evaluated the effectiveness of subcutaneous injection of sterile water compared to placebo in reduction of labor pain in 240 women:

– Pain scores were significantly lower for the sterile water intervention group compared to the control group at 10, 45 and 90 minutes after injections

IF IT HURTS, IS IT WORTH DOING?

– 83% of women said they would elect for sterile water injections again in future labours.

IS THERE ANY CHANCE OF IT INFLUENCING THE OUTCOME OF BIRTH?

– There was no difference between the women who received the sterile water injections and the women who received the placebo injection in terms of the end outcome of the labor for both the mothers and infants.

i.e no difference in rates of episiotomies, forceps, emergency C-sections etc.

References

Subcutaneous Sterile Water Injection for Labor Pain: A Randomised Controlled Trial.
Rai, R; Uprety, DK; Pradhan, T; Bhattarai, BK and Acharya, S.
Nepal Journal Of Obstetrics and Gynaecology: Vol 8, No 2 (2013).