Level 1: Likely reliable evidence
A Cochrane review of 11 randomized trials evaluated the safety and efficacy of water immersion during the first stage of labor (Cochrane Database Syst Rev. 2009;:CD000111). Water immersion, which involves complete abdominal submersion in a bath or pool, reduced both maternal pain and epidural and spinal analgesia requirements. Analgesia/anesthesia use was significantly lower for immersion groups compared with controls in a meta-analysis of six trials with 2,499 women (38.1% vs. 42.1%, P=.025, NNT 25). One high-quality trial with 120 women found that significantly fewer women in the immersion group experienced moderate to severe pain (67.8% vs. 90.2%, P=.004, NNT 5). There were no significant differences in labor duration, operative delivery rates, or neonatal outcomes.