Ive had a few bad calf cramps during the night over the past couple weeks also. So bad that the whole next day it hurts when I walk. I did some researching on the net and aparently its quite normal during pregnancy to have a few due to the amount of blood your pumping around but all you can do is try to keep your legs raised as much as you can to help the blood flow (this is during the night) as aparently it can pool in your legs. I plan to ask my Ob at my next appointment and see what he says.

Ive never got them during the day and its definitely not due to the cold as Im in perth and its really hot at the moment.