I had huge cramps with DS, esp. middle of the night and when waking up in the morning. This time I got only one leg cramp. I remembered how horrible it was last time and thought about why it was happening.
I realised something. In a non-pregnant state, you move around at night when you sleep. You roll over easily. You do it nearly subconsciousiously. So you don't really wake up, and you go back to deep sleep rather quickly.
Now, you are big, fat, uncomfortable (OK, at least I am!). At night, to roll over, you must lift your arms, pull your big belly, maybe even change the pillows from one side to the other, put them back between your knees... So, you wake up to do all this, and it takes a while to fall asleep again.
After a day or two your brain learns this. Even your sleeping brain. So what do you do? You stop moving. Your unconscious mind keeps you in the same position, and you end up stiff in bed. With leg cramps.
Choices: You could wake up more, move more often, and get less leg cramps. But end up more tired. Or you could stop moving so much, get stiff leg cramps, but get more sleep at night.
Well, I told my brain that this is what I was doing to myself. So now I wake up more, have to move the pillows... but I don't have leg cramps at all! Yes, I am more tired. But I quit work early (I have that luxury). Sometimes I give DS to DH when we get home, and take an extra nap to catch up on the sleep.
Who likes my theory?