Many women – almost half, in fact – suffer from leg cramps in pregnancy. These involuntary spasms usually begin to cause trouble at night during the second half of pregnancy.

The cramps mostly affect the calves. Some women find it difficult to sleep because of the pain from these leg cramps.

Considering leg cramps are so common in pregnancy you would expect there to be a well studied effective treatment. In fact there is surprisingly little research into this common problem. However the strongest evidence for any particular treatment relates to magnesium supplements. A Swedish study reported in 1995 found that magnesium tablets taken twice a day for three weeks were more effective than no treatment in reducing the frequency and severity of leg cramps. Women who had suffered from cramps every second night only got them once or twice a week after taking magnesium.

The only side effect of magnesium treatment reported was nausea but this was rare and mild if it occurred at all.

Other possible treatments studied for leg cramps in pregnancy are:

  • Calcium supplements,
  • Multivitamins,
  • Table Salt and
  • Tonic Water.

None of these have proved to be any better than no treatment. So sorry a Gin and Tonic won’t help.

Pretty much any magnesium supplement will be adequate for relief of leg cramps.

Finally I need to raise Deep Vein Thrombosis (DVT) or clots in the veins of the legs (also called Economy Class Syndrome when DVTs arise after air travel). DVTs are rare but there are a couple of reasons why they are more common in pregnancy than when you are not pregnant. In essence your blood is thicker in pregnancy (this is an evolutionary adaptation to prevent severe haemorrhage following childbirth) and the big lump in your abdomen can sometimes restrict the flow of blood back from your legs leading to stasis of blood in your leg veins and an increased chance of clotting.

DVTs cause leg pain and sometimes redness or visible swelling of the affected leg. They are more common on the right than the left. Accordingly all leg pain is not necessarily benign leg cramps. If your leg pain is constant, in one leg only (especially the right), or associated with swelling or redness you should call me immediately.

I thank my medical student Alex Owen for researching this topic and writing the first draft of this piece.