A New Mother and Father Are Upset That Their 2-Day-Old

A new mother and father are upset that their 2-day-old infant is requiring phototherapy for hyperbilirubinemia. The pediatrician who has followed the infant since birth is explaining the multiplicity of factors that can contribute to high serum bilirubin levels in neonates. Which of the following factors would the physician be most likely to rule out as a contributor?

A) The fact that the infant is being breast-fed
B) Hypoxia
C) Hepatic immaturity of the infant
D) Transitioning of hemoglobin F (HbF) to hemoglobin A (HbA)