A 5 week old breast fed baby whose birth weight was 3.5kg and is now 4.5kg is thriving well but is deeply jaundiced. What is the most likely diagnosis?

The key is B. Breast milk jaundice. [Breast milk jaundice is a type of neonatal jaundice associated with breastfeeding. It is characterized by indirect hyperbilirubinemia, presents in the first or second week of life, and can persist for as long as 12 weeks before spontaneous resolution. There is normal thrive and weight gain. In galactosemia there will be lethargy, vomiting, diarrhea and failure to thrive].