Aiyoh yes this is very common in pregnancy especially in third trimester, don't worry too much! It's usually because of low magnesium or calcium levels, so try to drink more water, eat more banana and dairy foods, and maybe ask your gynae if you can take magnesium supplement because it really helped me a lot when I had the same problem. But if the cramps are very severe, one sided, or got swelling and redness then please go see your gynae faster faster because want to rule out things like DVT which can be dangerous during pregnancy!