When a fetus has transposition of the great arteries are they unaffected til born?

True. They are unaffected until born .... This is because of the blood circulation system that is in place for the baby while still in utero. It isn't until after birth, that this circulation changes and from "fetal blood circulation" to "adult blood circulation." often times, these babies will have heart surgery with in just a few days of being born and go on to live very normal lives.
Yep. The fetal system is designed for growth & since it derives its oxygen from mom (doesn't breathe) the system bypasses the lungs & simply pumps to the body.After birth, circulation begins to bring the lungs on line & if the pipes are hooked up wrong, it shows up as a blue baby in trouble.Docs use meds to try to keep part of the bypass open, but urgent surgery is needed or baby may die.