Dahle 1995.

Methods	Double‐blind, parallel group RCT
Participants	73 pregnant women (mean 29 wk gestation) with rest cramps and no previous cramp treatment. Recruitment from Swedish prenatal care clinics.
Interventions	Either a chewable tablet containing 122 mg elemental magnesium ("primarily as Mg lactate or Mg citrate"), or matched placebo tablet, taken once each morning and twice each evening for 3 weeks
Outcomes	Primary outcome unclear. Change in cramp frequency on a 5‐point ordinal scale. Time of day cramps occurred on a 4‐point nominal scale. Presence of symptoms the day after a night of cramping on a 3‐point ordinal scale. Global patient assessment of treatment effect on a 5‐point ordinal scale. Cramp intensity on a visual analog scale (VAS). Serum magnesium and calcium and 24‐h urinary magnesium and calcium excretion
Notes	Published. Manufacturer sponsored. Did laboratory tests at only one of the two centres
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not described ("The patients were then randomly allocated to either magnesium or placebo")
Allocation concealment (selection bias)	Unclear risk	Not described. See above for only quote
Blinding (performance bias and detection bias) All outcomes	Low risk	Quote: “A magnesium‐placebo tablet batch of 90 numbered bottles was prepared by ACO Lakemedel...” Comment: Probably satisfactory, although pills were not described
Incomplete outcome data (attrition bias) All outcomes	Low risk	4/73 subjects dropped out of the study and were excluded from the analysis. Reasons for dropout were well described but treatment group was not identified. One placebo patient withdrew from treatment but appears (unclear) to have been included in the analysis. Comment: Probably adequate as total number of dropouts was small.
Selective reporting (reporting bias)	High risk	No description of outcomes by primary and secondary, and outcomes were incompletely described in methods, i.e. only in the results is it evident that before and after comparisons, mean differences and numbers attaining specific cut‐offs are used. Unclear how well outcomes were predefined. Inadequate reporting: no actual numbers for many P values. This study also reported a reduction in cramp frequency "from the initial average of every other day, to every 3 days in the placebo group and one to two times a week in the magnesium group (P < 0.05)". However, "every 3 days" and "one to two times a week" do not belong to the 5‐point ordinal scale used to measure this outcome (daily, every other day, twice a week, once a week, never).
Cramp diary (recall bias)	High risk	No diary used
Other bias	Unclear risk	Subjects treated differently at each site (one used laboratory testing, the other did not).