Transcutaneous electrical nerve stimulation for treatment of primary dysmenorrhea: A systematic review and meta-analysis of randomized controlled trials.

I 2 values were used according to the Cochrane Handbook for Systematic Reviews of Interventions, where 0% to 40% was not significant, 30% to 60% was moderate, 50% to 90% significant, and 75% to 100% highly significant.

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