We searched the Cochrane Pregnancy and Childbirth Group's Register (31 March 2015) and reference lists of retrieved studies.
SELECTION CRITERIA: Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy.
MAIN RESULTS: We included six studies (390 women). Four trials compared oral
magnesium with placebo/no treatment, two compared oral
calcium with no treatment, one compared oral
vitamin B versus no treatment, and one compared oral
calcium with oral
vitamin C. Two of the trials were well-conducted and reported, the other four had design limitations. The process of random allocation was sub-optimal in three studies, and blinding was not attempted in two. Outcomes were reported in different ways, precluding the use of meta-analysis and limiting the strength of our conclusions.The 'no treatment' group in one four-arm trial has been used as the comparison group for the composite outcome (intensity and frequency of leg
cramps) in
magnesium,
calcium, and
vitamin B versus no treatment. This gives it disproportionate weight in the overall analysis, thus interpretation of these results should be cautious. Oral
magnesium versus placebo/no treatmentMagnesium (taken orally for two to four weeks) did not consistently reduce the frequency of leg
cramps compared with placebo or no treatment. Outcomes that showed differences were: frequency of leg
cramps after treatment: never, and twice a week (risk ratio (RR) 5.66, 95% confidence interval (CI) 1.35 to 23.68, one trial, 69 women, evidence graded low; RR 0.29, 95% CI 0.11 to 0.80, one trial, 69 women), and frequency of leg
cramps: 50% reduction in number of leg
cramps after treatment (RR 1.42, 95% CI 1.09 to 1.86, one trial, 86 women, evidence graded low). The outcomes that showed no difference were: frequency of leg
cramps during two weeks of treatment (mean difference (MD) 1.80, 95% CI -1.32 to 4.92, one trial, 38 women, evidence graded low); frequency of leg
cramps after treatment: daily, every other day, and once a week (RR 1.20, 95% CI 0.45 to 3.21, one trial, 69 women; RR 0.44, 95% CI 0.12 to 1.57, one trial, 69 women; RR 1.54, 95% CI 0.62 to 3.87, one trial, 69 women).Evidence about whether
magnesium supplements reduced the intensity of
pain was inconclusive, with two studies showing that it may slightly reduce
pain, while one showed no difference. There were no differences in the experience of side effects (including
nausea,
flatulence, diarrhoea and intestinal air) between pregnant women receiving
magnesium compared with placebo/no treatment. Oral
calcium versus no treatmentA greater proportion of women receiving
calcium supplements experienced no leg
cramps after treatment than those receiving no treatment (frequency of leg
cramps after treatment: never RR 8.59, 95% CI 1.19 to 62.07, one study, 43 women, evidence graded very low). There was no difference between groups for a composite outcome (intensity and frequency) for partial improvement (RR 0.64, 95% CI 0.36 to 1.15, one trial, 42 women); however, the same trial showed a greater proportion of women experiencing no leg
cramps after treatment with
calcium compared with no treatment (RR 5.50, 95% CI 1.38 to 21.86).Other secondary outcomes, including side effects, were not reported. Oral
vitamin B versus no treatment Frequency of leg
cramps was not reported in the one included trial. According to a composite outcome (frequency and intensity), more women receiving
vitamin B fully recovered compared with those receiving no treatment (RR 7.50, 95% CI 1.95 to 28.81). Those women receiving no treatment were more likely to experience a partial improvement in the intensity and frequency of leg
cramps than those taking
vitamin B (RR 0.29, 95% CI 0.11 to 0.73, one trial, 42 women), or to see no change in their condition. However, these results are based on one small study with design limitations.Other secondary outcomes, including side effects, were not reported. Oral
calcium versus oral
vitamin CThere was no difference in the frequency of leg
cramps after treatment with
calcium versus
vitamin C (RR 1.33, 95% CI 0.53 to 3.38, one study, 60 women, evidence graded very low). Other outcomes, includingside effects, were not reported.
AUTHORS' CONCLUSIONS: It is unclear from the evidence reviewed whether any of the interventions (oral
magnesium, oral
calcium, oral
vitamin B or oral
vitamin C) provide an effective treatment for leg
cramps. This is primarily due to outcomes being measured and reported in different, incomparable ways, and design limitations compromising the quality of the evidence (the level of evidence was graded low or very low). This was mainly due to poor study design and trials being too small to address the question satisfactorily.Adverse outcomes were not reported, other than side effects for
magnesium versus placebo/no treatment. It is therefore not possible to assess the safety of these interventions.The inconsistency in the measurement and reporting of outcomes, meant that data could not be pooled, meta-analyses could not be carried out, and comparisons between studies are difficult.The review only identified trials of oral interventions (
magnesium,
calcium,
vitamin B or
vitamin C) to treat leg
cramps in pregnancy. None of the trials considered non-
drug therapies, for example, muscle stretching,
massage, relaxation, heat
therapy, and dorsiflexion of the foot. This limits the completeness and applicability of the evidence.Standardised measures for assessing the frequency, intensity and duration of leg
cramps to be used in large well-conducted randomised controlled trials are needed to answer this question. Trials of non-
drug therapies are also needed.