The effect of oral magnesium substitution on pregnancy-induced leg cramps

OBJECTIVE: Our purpose was to determine whether women with pregnancy-related leg cramps would benefit from oral magnesium supplementation. STUDY DESIGN: Seventy-three women with pregnancy-related leg cramps were interviewed about their symptoms in a prospective, double-blind, randomized trial. Initial serum magnesium levels and diurnal magnesium excretion was determined in 50% of the patients. Oral magnesium or placebo was given for 3 weeks, after which new interviews and laboratory analyses were performed. RESULTS: Serum magnesium levels in these patients were at or below the lower reference limit, as is also often the case in healthy pregnant patients. Oral magnesium substitution decreased leg cramp distress (p< 0.05 compared with the placebo group, p< 0.001 compared with initial complaints), but did not significantly increase serum magnesium levels, excess magnesium being excreted as measured by an increase in urinary magnesium levels (p< 0.002). CONCLUSION: Oral magnesium supplementation seems to be a valuable therapeutic tool in the treatment of pregnancy-related leg cramps.