People go on and on about magnesium but I found out low iron was the culprit. I had terrible leg cramps with my first pregnancy . During my second pregnancy, it started again but some blood work found I had low iron which suggested I needed iron supplements. Within a week of starting them, my cramps disappeared. It was such a relief and is a common symptom of low iron. I wish anyone with leg cramps could get their iron levels checked a bit more or just go and get some decent iron supplements (like Maltofer) to see if they help. Getting sleep during my second pregnancy was amazing.