http://www.babycenter.com/0_leg-cramps-during-pregnancy_250.bc

"Why am I having leg cramps during pregnancy?

No one really knows why women have more leg cramps when they're pregnant. It's possible that your leg muscles are tired from carrying around all of your extra weight. Or they may be aggravated by the pressure your expanding uterus puts on the blood vessels that return blood from your legs to your heart and the nerves that lead from your trunk to your legs.

Leg cramps may start to plague you during your second trimester and may get worse as your pregnancy progresses and your belly gets bigger. While these cramps can occur during the day, you'll probably notice them most at night.

How can I prevent these cramps?

Try these tips for keeping leg cramps at bay:

•  Avoid standing or sitting with your legs crossed for long periods of time.

•  Stretch your calf muscles regularly during the day and several times before you go to bed.

•  Rotate your ankles and wiggle your toes when you sit, eat dinner, or watch TV.

•  Take a walk every day, unless your midwife or doctor has advised you not to exercise.

•  Avoid getting too tired. Lie down on your left side to improve circulation to and from your legs.

•  Stay hydrated during the day by drinking water regularly.

•  Try a warm bath before bed to relax your muscles.

•  There's some evidence that taking a magnesium supplement in addition to a prenatal vitamin may help some women. Check with your provider before taking any kind of supplement during pregnancy.

You may have heard that having leg cramps is a sign that you need more calcium, and that calcium supplements will relieve the problem. Though it's certainly important to get enough calcium, there's no good evidence that taking extra calcium will help prevent leg cramps during pregnancy. In fact, in one well-designed study, pregnant women taking calcium got no more relief from leg cramps than those taking a placebo.

What's the best way to relieve a cramp when I get one?

If you do get a cramp, immediately stretch your calf muscles: Straighten your leg, heel first, and gently flex your toes back toward your shins. It might hurt at first, but it will ease the spasm and the pain will gradually go away.

You can try to relax the cramp by massaging the muscle or warming it with a hot water bottle. Walking around for a few minutes may help too.

What if the pain persists?

If your muscle pain is constant and not just an occasional cramp — or if you notice swelling or tenderness in your leg — call your practitioner. These may be signs of a blood clot, which requires immediate medical attention. Blood clots are rare, but your risk is higher during pregnancy."