Eight RCTs were included in the review (n=828 women). One RCT scored 13 points on the validity assessment; two RCTS scored 12, four RCTs scored 10, and one RCT scored 8 points. The authors reported that some of the trials were not blinded.
Caesarean rates: Sterile water injection significantly reduced the risk of having a caesarean section (RR 0.51, 95% CI 0.30 to 0.87; eight RCTs, n=828 women) compared with placebo or alternative therapy. There was no evidence of significant statistical heterogeneity (I2=0%).
Pain: Sterile water injection significantly reduced pain (measured on Visual Analogue Scale) at: 10 to 30 minutes (WMD -26.04mm, 95% CI -34.14 to -17.94; four RCTs, n=289); 45 to 60 minutes (WMD -36.27mm, 95% CI -50.80 to -21.74; five RCTs, n=542 women); and at 90 to 120 minutes (WMD -27.74mm, 95% CI -39.03 to -16.45; five RCTs, n=488 women) compared with placebo or alternative therapies. There was evidence of significant statistical heterogeneity at all time points (65% at 10 to 30 minutes, 94% at 45 to 60 minutes and 86% at 90 to 120 minutes).
There were no significant differences between groups on use of regional analgesia or anaesthesia or subjective rating of the intervention.