A lot of different things can cause
Jaundice...it can spontaneously occur, and it can occur from different blood-type issues..for instance, my son had it because he has A+ blood but I have O+ and somehow our blood mixed, and the antibodies in my blood attacked his red blood cells :(. It caused him to have what's caused ABO Incompatibility Jaundice...and his levels were dangerously high very soon after birth, which is how they noticed it immediately and were able to identify it.