My kids are much older but something about the experience of rearing babies and toddlers changed my sleep permanently: I sleep much lighter (read: woken up by every noise and movement), and the whole concept of "sleeping in" has vanished as a possibility, even if I go to bed very late and no one else is in the house.

Of course it's a trade-off I'd gladly make again but it still sucks that I will never feel as well rested day-to-day as I did before kids.