Leg cramps can occur during pregnancy, especially while you sleep. They may be a signal that your body is lacking potassium or calcium. Drink plenty of milk, eat dairy products like yogurt and cheese, and enjoy multiple fruits and vegetables. Also, leg cramps at night are common because of sleep position. If you sleep on your back, the covers may pull your toes down and in this position your calves will cramp. Make sure you sleep on your left side. If your legs cramp during the day, try some gentle stretching exercises. Also, walking 30 to 40 minutes a day helps strengthen your legs. As your muscles get stronger, they will cramp less readily.