I didn't notice much change after the first two kids, but after baby #3 they definitely changed. The first couple were mild, then I had a run of heavy, crampy ones with an additional 'made of concrete' all over feeling. I also got a new 25ish day cycle when it used to be about a week longer. I felt so ripped off I even went to the Dr to complain lol.

It has settled down and is my normal 'oh, a bit of blood' ones now but apparently I am keeping the stupidly short cycle.