The analgesic efficacy of subcutaneous injection of sterile water compared to isotonic saline was investigated in a randomized, controlled study on a total of 100 women in the active phase of labor and who complained of low back pain. Pain perception was rated on a numerical rating scale before and at 10 and 45 minutes after the injection. The initial pain score was the same in both groups and pain relief was expressed by both groups irrespective of the solution injected, but the sterile water group had significantly higher relief scores compared to those receiving saline. This was not influenced by maternal age, parity, education, body mass index, cervical dilatation at intervention or fetal size, suggesting that subcutaneous injection of sterile water to the lower back provides relief from back pain during labor.