I had two fathead babies (for their gestations) and I'm still in one piece I'll admit that I did tear pretty badly with DD, but I attribute that to having an epidural and pushing past when I should have.

The others are right, the plates slide over each other to make the head mold better. That's why the majority of vaginally-birthed babies have funny shaped heads Thats something else that makes me think I pushed to hard with DD, she had a normal shaped head and I don't think I have her head time to change shape...