Summary of findings 2. Magnesium for pregnancy‐associated leg cramps.

Magnesium compared with placebo for skeletal muscle cramps
Patient or population: pregnant women with leg cramps Settings: outpatients recruited through obstetrical care providers Intervention: magnesium supplements (oral) Comparison: placebo
Outcomes	Illustrative comparative risks* (95% CI)		Relative effect (95% CI)	No. of participants (studies)	Quality of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Placebo	Magnesium
Cramp frequency (percentage change from baseline at 4 weeks)	None of the 3 relevant studies measured cramp frequency in a way that permitted pooling of data. 1 study found benefit, 1 study was uninterpretable, and 1 study (the only 1 of the 3 that was not rated high risk of bias) trended in favor of placebo. Taken collectively, no conclusions can be drawn.			204 (3 studies)	⊕⊝⊝⊝ very lowa due to very serious risk of bias, inconsistency, and imprecision	Whether or not magnesium supplementation reduces cramp frequency in pregnant women is uncertain
Cramp frequency (responder analysis: 25% or better reduction at 4 weeks)
Cramp frequency (mean number of cramps per week on treatment at 4 weeks)
Cramp intensity (moderate or worse at 4 weeks)	None of the studies reported cramp intensity in a way that permitted this to be determined.			No studies	No evidence
Cramp duration (≥ 1 minute at 4 weeks)	None of the studies reported cramp duration			No studies	No evidence
*The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: Confidence interval; RR: Risk Ratio
GRADE Working Group grades of evidence High quality: further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: we are very uncertain about the estimate.

^aDowngraded twice for very serious risk of bias given 2 of the 3 studies were considered at high risk of bias; downgraded once for inconsistency given 1 study reported benefit and another trended towards harm; and downgraded once for imprecision given all studies were relatively small (largest had 86 participants) and none could be pooled.