There isn't a clear answer as to why women experience sharp cramps (or "charley-horses") in their calf muscles, mostly at night toward the end of pregnancy, but doctors have several theories:
• Nerve pressure: As your uterus expands it can put pressure on certain nerves, causing painful spasms in your legs.
• Poor circulation: The pressure your growing belly puts on blood vessels in your legs can disrupt circulation and cause cramps.
• Dehydration: Sometimes muscle pain can be caused by dehydration, so be sure you're drinking enough fluids (at least six to eight glasses a day).
When a cramp strikes, gently stretching your calf muscle can help. To do this, straighten your leg and flex your foot (heel down, toes up). It may be tempting to point your toes, but this usually just makes the pain worse. Since it can be hard to reach your lower leg with that burgeoning belly, ask your husband to massage the area using long, firm strokes down toward your foot.
Although there isn't a whole lot you can do to prevent these spasms, here are some tips that may help:
• Flexing and releasing each foot a few times before bed to stretch the calf muscles.
• Taking short walks every day (with your doctor's permission) to boost circulation.
• Avoiding standing or sitting with your legs crossed for long periods, which can slow circulation.
• Taking a warm (not hot) bath before bed; this gets circulation going and may prevent cramps while you sleep.
While annoying and painful, these cramps are usually not dangerous for your baby, and tend to come and go quickly. But if they persist, or your leg begins to swell or feel warm, let your doctor know. This can be a sign of a blood clot, which is very rare, but does require treatment.