BACKGROUND: Intracutaneous or subcutaneous injection of sterile water is rapidly gaining popularity as a method of pain relief in labour and it is therefore essential that it is properly evaluated. Adequate analgesia in labour is important to women worldwide. Sterile water injection is inexpensive, requires basic equipment, and appears to have few side effects. It is purported to work for labour pain. OBJECTIVES: To determine the efficacy of sterile water injections for relief of pain (both typical contraction pain and intractable back pain) during labour compared to placebo (isotonic saline injections) or non-pharmacological interventions, and to identify any relevant effects on mode and timing of delivery, or safety of both mother and baby. SEARCH METHODS: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 May 2011), MEDLINE, and EMBASE (January 2010 to 30 May 2011), together with reference lists in retrieved studies and review articles. SELECTION CRITERIA: We included randomised, double blind, controlled studies using intracutaneous or subcutaneous sterile water injections for pain relief during labour. There were no restrictions on birth place, parity, risk, age, weight, gestation, or stage of labour. Potential comparators were placebo (saline) and non-pharmacological interventions (e.g. hypnosis or biofeedback). DATA COLLECTION AND ANALYSIS: Two review authors independently assessed eligibility and quality of trials, and extracted data. We resolved any disagreements or uncertainties by discussion with a third review author. Primary outcome measures were at least 50% pain relief, or at least 30%, pain relief, patient global impression of change of at least 'good', mode of delivery, perinatal morbidity and mortality, maternal complications and adverse events. Secondary outcomes were women with any pain relief, use of rescue analgesia, and treatment group average pain relief. We made explicit judgements about potential biases in the studies. MAIN RESULTS: We included seven studies, with 766 participants: four used intracutaneous injections, two subcutaneous, and one both. All reported on low back pain in labour only. Methodological quality was good, but four studies were at high risk of bias due to small size of treatment groups, incomplete outcome data, and performance bias.All studies reported treatment group mean or median scores, finding greater reduction in pain for sterile water. However, failure to demonstrate a normal distribution for pain intensity or relief, and use of different scales, meant meta-analysis was inappropriate. No study reported primary dichotomous efficacy outcomes. One reported the number self-scoring 4/10 cm or more reduction in pain; significantly more had this outcome with sterile water (50% to 60%) than with placebo (20% to 25%).There was no significant difference between sterile water and saline for rates of caesarean section (risk ratio (RR) 0.58, 95% confidence interval (CI) 0.33 to 1.02), instrumental delivery (RR 1.31, 95% CI 0.79 to 2.18), rescue analgesia (RR 0.86, 95% CI 0.44 to 1.69), timing of delivery, or Apgar scores. Two studies reported that more women treated with sterile water would request the same analgesia in future.No study reported on women's satisfaction with pain relief, women's sense of control in labour, women's satisfaction with the childbirth experience, mother/baby interaction, rates of breastfeeding, maternal morbidity, infant long-term outcomes, or cost. No adverse events were reported other than transient pain with injection, which was worse with sterile water. AUTHORS' CONCLUSIONS: The outcomes reported severely limit conclusions for clinical practice. We found little robust evidence that sterile water is effective for low back or any other labour pain. Neither did we find any difference in delivery or other maternal or fetal outcomes. Further large, methodologically rigorous studies are required to determine the efficacy of sterile water to relieve pain in labour.