Ooh, I had KILLER leg cramps in my first pregnancy. Mostly at night, but even in labor - honestly what I remember as inconcievably painful from that birth was not actually *having* the baby, it was the cramps. It was like getting hit by a truck. Only thing I could do was keep waving my legs around in the air - midwives and husband got kicked in the head a lot but I did not care if it kept some of the cramps from taking hold. Oy!
If you are anemic it is almost guaranteed that is a big part of the problem, so when that improves the leg cramps may too.
Potassium did not seem to be an issue for me, nor magnesium, and boy did I get tired of the "oh just eat more bananas" brigade
The three things that DID help for me, somewhat during that pregnancy and I attribute my much reduced severity of leg cramps in my second full pregnancy, were:
1) never getting the least bit dehydrated. Drinking a couple big glasses of water between dinner and bed helped.
2) not overdoing calcium -- I *love* milk, would drink a gallon a day given the chance
, but had a lot more and worse cramps if I exceeded about 3-4 cups per day.
3) frequent exercise to get circulation going during the day and especially in the evening -- whicj really did help (on sedentary days, cramps were worse) BUT I will say that tiny bits of nighttime exercise, like walking to bathroom or bicycling legs in bed to ward off developing cramp - actually seemed to incerase cramping for the following hour or so, dunno why.
Good luck and complete sympathies,
Pat