Sterile Water Injections

What are Sterile Water Infections?

Injections of sterile water in the lower back, used to decrease back pain in labor.

Sterile water injections (SWI) are an effective method for the relief of back pain in labour. The procedure involves a small amount of sterile water (0.1 ml to 0.2 ml) injected under the skin at four locations on the lower back (sacrum).

The injections cause a brief but intense stinging sensation, like a wasp sting, that lasts for about 30 seconds and then wears off completely. As the stinging sensation eases, relief from the back pain is felt. To distract from the stinging sensation the injections are done during a contraction by two midwives. Women benefit from support and encouragement as the injections are being given.

SWI provides effective pain relief for up to 85 percent of women with back pain in labor and can last for up to two hours.

What are the benefits of SWI?

• often immediate effect
• no effect on mother’s state of consciousness
• no effect on baby
• does not limit mobility
• does not adversely affect labor progress
• is a simple procedure that can administered by your midwife
• can be repeated as needed.

SWI are an excellent alternative for relief of back pain in labour. Though SWI will not provide pain relief from contraction pain, once the back pain is alleviated, you may cope better with labor pain. As the back and pelvic muscles relax following the relief of pain, this may assist with the progress of your labor.

Sterile water injected lateral to the lumbosacral spine in women with severe low back pain during labor substantially reduces pain and decreases the rate of Cesarean deliveries, according to a meta-analysis published in the August issue of BJOG: An International Journal of Obstetrics and Gynaecology.

To investigate the therapeutic effect of the injections, the research team conducted a literature search that turned up 8 randomized, controlled trials (n = 828) comparing outcomes associated with sterile water injections with placebo (injection of isotonic saline), acupuncture, or transcutaneous electric nerve stimulation.

In all eight studies combined, sterile water cut the Cesarean section rate by half: 4.6% in the sterile water group and 9.9% in the comparison group (relative risk = 0.51).

The reports documented significant reductions in visual analog pain “TAJE scores of sterile water compared with all other interventions. The weighted mean differences were -26 at 10-30 minutes, -36 at 45-60 minutes, and -28 at 90-120 minutes.

Dr. Hutton’s team theorizes that the pain reduction from water injections may increase parasympathetic tone; enhance relaxation, which promotes fetal rotation to a more favorable position for vaginal delivery, and “decreases the urgency for a cesarean section and allowed for a long enough time for labor to progress normally.”  

Sterile-water injection causes a burning sensation that is much more painful than saline injection and is thought to relieve labor pain by counterirritation. Four RCTs included in one review found a significant reduction in back pain for 45 to 90 minutes based on a visual analog scale. Three of the trials found that women who received injections of sterile water were more interested in receiving the injections in a subsequent labor than women who received saline injections. None of the trials showed a decrease in requests for pain medicines, perhaps because of the limited time of effectiveness or a lack of effectiveness for abdominal labor pain.


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