Leg cramps are experienced as sudden, intense involuntary contractions of the leg muscles. They are a common problem in pregnancy, especially in the third trimester. They are painful and can interfere with daily activities, disrupt sleep, and reduce quality of life. Various interventions have been used during pregnancy to treat leg cramps, including drug, electrolyte (magnesium, calcium, sodium) and vitamin therapies, and non-drug therapies such as muscle stretching. The goal of this review was to find out what is effective and safe for treating leg cramps during pregnancy.
We included six randomised controlled studies, with a total of 390 women who were 14 to 36 weeks pregnant, comparing either magnesium, calcium or vitamin B with placebo or no treatment, and comparing vitamin C with calcium. All treatments were given as tablets to be chewed or swallowed.
Magnesium supplements did not consistently reduce how often women experienced leg cramps when compared with placebo or no treatment. Studies measured this in different ways, sometimes showing that magnesium helped reduce the number of leg cramps but sometimes showing that it made no difference. Likewise, evidence about whether magnesium reduced the intensity of pain was inconclusive with one study showing a reduction while others showed no difference. There was no difference in the experience of side effects, such as nausea and diarrhoea.
A greater proportion of women receiving calcium experienced no leg cramps after treatment compared to women who did not receive any treatment, however another measure of improvement showed no difference between the groups.
More women who received vitamin B supplements fully recovered compared with those women receiving no treatment; however these results were from a small sample within a study with design limitations.
The frequency of leg cramps was no different between women treated with calcium and those treated with vitamin C.
The level of evidence was graded low or very low. This was mainly due to the small sample size of studies and poor study design. Two studies were well-conducted and reported. The other four had design limitations: women were not allocated to different treatment groups in the best way in several studies, and in two studies women knew whether they were receiving treatment or not. Adverse effects such as any effect of the treatment on pregnancy complications, labour and the baby were not reported. Several of the studies focused mainly on serum calcium and magnesium levels. The frequency and intensity of cramps and the duration of pain were not reported in a consistent way and often information was lacking on how they were measured, either during treatment, at the end of treatment or after treatment had stopped.
It is not clear from the evidence reviewed whether any of the oral interventions (magnesium, calcium, vitamin B or vitamin C) provide an effective and safe treatment for leg cramps in pregnancy. Supplements may have different effects depending on women's usual intake of these substances. No trials considered therapies such as muscle stretching, massage, relaxation or heat therapy.
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.
Leg cramps are a common problem in pregnancy. Various interventions have been used to treat them, including drug, electrolyte and vitamin therapies, and non-drug therapies.
To assess the effectiveness and safety of different interventions for treating leg cramps in pregnancy.
We searched the Cochrane Pregnancy and Childbirth Group's Register (31 March 2015) and reference lists of retrieved studies.
Randomised controlled trials (RCTs) of any intervention (drug, electrolyte, vitamin or non-drug therapies) for treatment of leg cramps in pregnancy compared with placebo, no treatment or other treatment. Quinine was excluded for its known adverse effects (teratogenicity). Cluster-RCTS were considered for inclusion. Quasi-RCTs and cross-over studies were excluded.
Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy.
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 treatment
Magnesium (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 treatment
A 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 C
There 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, including side effects, were not reported.