Babies develop jaundice because of several reasons. Some babies get jaundice from the breakdown of blood due to bruising at birth or superficial blood clots on the scalp. These blood clots are due to unavoidable pressure on the scalp as the baby passes through the birth canal. Others have a blood group that is different from the mother’s; the antibodies present in the mother may attack the baby’s own red blood cells, causing the baby to be jaundiced.
Some babies have an inherited glucose-6-phosphate dehydrogenase (G6PD) deficiency that predisposes them to onset jaundice. G6PD is an enzyme in the body that helps red blood cells function normally (see G6PD deficiency). Occasionally, babies develop jaundice because of an infection of the urinary system or blood.
Prolonged jaundice lasting for more than two weeks could be due to an infection, breast-milk jaundice, abnormal bile ducts or a metabolic disease. Some metabolic diseases are detected with metabolic screening.
In many babies, an underlying cause may not always be found. It is common for the doctor to take further blood samples from your baby even after knowing the bilirubin level, in order to find out the cause of jaundice.