Sterile Water Injections: Do They Work?

The United Kingdom health authorities now recommend sterile water injections for women in labor to reduce back pain. However, not everyone is convinced about their effectiveness.

About 30% of women experience intense lower back pain while giving birth, likely due to the baby being in a posterior or sunny-side-up position.

The updated guidelines of the U.K. National Institute for Health and Care Excellence (NICE), the National Healthcare System (NHS) watchdog, now include sterile water injections (SWIs) as a pain relief option for women with back labor.

The new method prompted criticism from some healthcare professionals and commentators, going as far as calling it "pseudoscience." However, sterile water injections for back pain are commonly used in Sweden and are a method endorsed by some maternal care experts.

What are sterile water injections?

Sterile water injections involve administering 0.1ml or 0.5ml of water free of contaminants and harmful additives into the woman's lower back via four injection points. The water can be administered within the layers of the skin or under the skin, forming small blisters.

Because the injections are painful, they are usually given at the height of a contraction.

Although the exact mechanisms of action remain unclear, scientists think that sterile water injections may prevent pain signals from reaching the brain.

Another possible explanation is that irritation in the skin caused by the injection provokes changes in certain nerve fibers, resulting in endorphin release, similar to TENS machines. Or it could be that sterile water injections work as a physiological distraction.

How effective are sterile water injections?

The evidence on the effectiveness of sterile water injections is mixed. For example, a 2012 review of seven randomized, double-blind, controlled trials that included 766 participants did not find good quality evidence that sterile water injections during labor are effective.

A 2020 clinical trial included over 1,100 women, half of whom received SWI during delivery. Although the injections did not reduce rates of cesarean delivery, significantly more women receiving SWIs reported a reduction in pain compared to placebo up to 90 min following the administration.

At 30 minutes after the injection, 60.8% of women in the SWI group and 31.4% of women in the placebo group reported a 30% reduction in self-reported pain.

Nearly half (43.3%) of women who received sterile water injections and 18.1% of women on the placebo reported a 50% reduction in back pain.

Dr. Nicholas Barrett, a consultant in critical care medicine at Guy's and St Thomas' NHS Foundation Trust, points out that the trial excluded women who were "not coping with pain," potentially impacting the findings. Moreover, the data on pain beyond the 30-minute interval is scarce.

Dr. Virginia Stulz, an associate professor of midwifery at Western Sydney University, says that sterile water injections don't pose any side effects for mothers or babies except for an intense stinging on administration.

"They are very good for back pain and prevent the woman from going on to have an epidural. Women have reported that they have instant pain relief without any side effects. Women have reported that receiving the SWI during a contraction makes it more bearable," she tells Healthnews.

Professor Sally Collins, the lead author of the 2020 study, said the use of SWIs has multiple benefits, especially in developing countries.

"The fact that it is cheap, simple, and needs minimal training should mean it will be able to provide pain relief for women in developing countries where access to other pain relief may be limited," she said in a statement.

What do leading organizations say?

During the consultation phase, the U.K.'s Obstetric Anaesthetists' Association asked the NICE for a "possible biologically plausible explanation" for the use of sterile water injections for back labor.

"Because it is cheap and unlikely to cause harm, is an inadequate justification for a recommendation, especially as NICE does not recommend other similar non-pharmacological therapies such as acupuncture and hypnosis," the organization said.

According to the American College of Obstetricians and Gynecologists (ACOG) guidelines, most women in labor can be offered a variety of nonpharmacologic techniques, including sterile water injections.

Although none of them have been found to have adverse effects on women of the fetus, evidence is insufficient to determine their effectiveness, the ACOG says.

Pros and cons of sterile water injections

You don't need to decide about a pain relief method until you are actually in labor. Nevertheless, consider discussing the options with your healthcare provider before giving birth.

The pros of sterile water injections include:

• A very low price as it only requires sterile water, a disposable syringe, and a short needle.
• SWIs are safe for most women and their babies.

The cons of SWIs are the following:

• Pain caused by administration of the injection.
• The effect is short-term.
• Only relieves back labor but not other pain.

The NICE's guidelines recommend sterile water injections only as a back labor relief option, not a replacement for epidural, opioids, and other well-established methods to reduce pain.