Answer: Legs often swell during pregnancy because the pressure of your expanding uterus slows the blood returning from your legs to your heart.
You may first develop leg cramps during your second trimester, and they may get worse as your pregnancy progresses and your belly gets bigger. These cramps can occur during the day, but you'll probably notice them most at night because they can interfere with your ability to get a good night's sleep.
These steps work whenever you have a leg cramp:
Stretch your calf muscles immediately by straightening your leg, heel first, and gently flexing your toes back toward your shins. (Don't point your toes while stretching. It can make the muscle contract and worsen the cramp.) This stretch might hurt at first, but it will ease the spasm and gradually make the pain go away.
After you stretch, massage the muscle or warm it with a hot water bottle to relax the tissue. Walking around for a few minutes may help too.
Take a walk every day (unless your healthcare provider has advised you not to exercise).
Lie down on your left side to improve circulation to and from your legs.
Drink water regularly to stay hydrated during the day.
Try a warm bath before bed to relax your muscles.