Yes, mine started at four months. Dd just turned five months and I think it is finally slowing down. With looong dark hair, it means a hairball every time I brush it. Two every time I wash it. It clogs the vacuum.

My only problem is that I'd wanted to cut it to donate before this started, but I was afraid I would freak out post-partum if I cut off a foot or so. Oh, well. So now I need to look for hairstyles for, well, thinner hair.