Hilary Duff, all grown up. (John Carucci/AP)

The actress and young adult novelist announced the sex of her baby on an episode of “The Ellen DeGeneres Show,” set to air Monday, according to USA Today. The former Disney star said she’s four months along.

“It's kind of like a little alien has taken over your body,” Duff, 24, said of the pregnancy. “You just don't quite feel normal. But it's cool. It's been good.”

If your first reaction to this news is, “I’m old,” you’re not alone. Duff told the Associated Press she’s seen that reaction on Twitter:

“The truth is that I’m very young and things in my life have happened very fast. I guess, why stop now?”

Duff is married to hockey player Mike Comrie. The couple announced the pregnancy this August.