Midwife Nikki replies: This is common in the middle months and often gets worse as your pregnancy progresses, due to the extra weight you're carrying. The cramps tend to occur more at night and may be aggravated by the pressure your growing uterus puts on the blood vessels between your legs and your heart.
Try lying on your left side, which can help improve circulation in your legs and reduce cramp, and if you do get a cramp, stretch your calf muscles, flexing your toes towards your shins. Massaging the calf muscle can also help, as can applying a warm hot water bottle to the area. Leg cramps can be reduced by avoiding sitting cross-legged for long periods of time and ensuring you get enough exercise. There's a theory that too little calcium and potassium circulating in your blood can cause muscle spasms, so to boost your levels a good tip is to eat a banana and/or try drinking a glass of milk just before you go to bed.