water injections - intradermal water blocks

Water injections

Intradermal water blocks

Intra-dermal water blocks are useful in relieving back pain during labor in up to 90% of women. However, water blocks do not lead to the reduction in the number of requests for epidurals, indicating that the relief they bring is not significant.

About third of laboring women have back pain which is qualitatively different from pain associated with contractions. In fact, there are two kinds of back pain during labor, and patients often describe them as pain of contraction shooting to the back and “riding on” another, continuous low-back pain, so that both together become really intense. It is thought that continuous low-back pain is caused by the stretching and pressure in the areas surrounding the uterus, in contrast to the rhythmic pains that are clearly related to contractions.

One of the ways that may relieve this pain is injection of water under the skin in the lower back, or intradermal water blocks. To describe them in short, about 0.5 to 1 ml of water is injected at four locations in the small of the back. It seems that the precise location of these injections does not appear to be crucial to the success. The effect lasts for anything from 45 minutes to 2 hours, after which the injections may be repeated. The injections sting for a few seconds and form small wheals that gradually disappear. Though normal saline injection causes much less injection pain than plain water, its effects are also less impressive.

Precisely how these injections work is unknown, and some doctors have suggested that it is a form of counter-irritation, in which pain in one part of the body can be relieved by painful irritation of the skin near or away from the painful area. Another theory proposes that the initial stinging may interfere with the transmission of pain signals to the central nervous system from the deeper tissues of the low back. This fits into so called gate control theory of pain, according to which impulses entering the brain compete with each other. That’s why it helps to relieve pain by rubbing the painful area. There is also some evidence that sticking a needle under the skin increases the amount of endorphins, the substances that act like morphine and other opiates and are produced in the brain and the spinal cord. Similar to the way acupuncture works.

Intra-dermal water blocks have been used in Scandinavia since the mid-seventies for relieving the pain of renal colic, chronic neck and shoulder pain and other pain syndromes.

Water blocks bring some relief to laboring women and may block back pain in as many as 90% of patients. Many women who had these blocks say that they would use them in the next labor. Unfortunately, the relief provided is not very significant, and in clinical trials studying them the number of requests for other methods of pain relief does not change.

In conclusion, even though intra-dermal water blocks reduce severe back pain, their value in reducing overall pain in labor is limited.


1. Simkin PP, O’Hara M. Nonpharmacologic relief of pain during labor: Systematic reviews of five methods Am J Obstet Gynecol 2002; 186:S131-59.



Dr. Eugene Smetannikov is a practicing anesthesiologist with the interest in obstetric anesthesia. He is the author of the most comprehensive book on the subject, The Truth About Labor Epidural