At how many weeks did your baby turn head down..?

I'm currently 30 weeks and my Dr. Is trying to schedule a c section. If by the next time I go to my appointment and she has not turned yet. She weighs 3lbs 3oz. Everything at the moment is fine with my baby beside that she has a two vessel cord. So I don't see why I would need a c section if ive had my 3 boys natural.. How many weeks were you when your baby turn head down..??