Dr. Greene, my 6-week old was diagnosed with breastfed jaundice when her bilirubin was taken at one week old. I am supposed to stop breastfeeding her for 24 hours (and give her formula) and am finding her resisting the bottle. Will the jaundice eventually go away and could there be any harm in not giving her the recommended 24-hour break from breastfeeding?

This week, while I was putting up lights to decorate for the holidays, I bruised my arm. I can remember, as a young child, watching bruises transform through a series of colors before they eventually disappeared.

Hemoglobin, the red pigment in red blood cells, must undergo a succession of changes before the body can dispose of it. Specific enzymes from our great processing center, the liver, carry out each step. Bilirubin, the yellow pigment responsible for jaundice, is a normal component in the breakdown of hemoglobin. Adults often turn yellow when they have hepatitis because their livers aren't able to process the bilirubin.

Every day, about 1% of our red blood cells expire, to be replaced by fresh, young ones ready to carry oxygen to supply the body. Our lifeblood is new every 4 months.

A low level of bilirubin (about 1 mg/dL) circulates throughout our bodies as part of this process. This concentration is too faint to be visible.

Even before babies are born, this renewing of the blood is taking place. The placenta carries away the bilirubin as it is formed. After babies are born, they enter a transition period as their livers begin to assume this responsibility. Often, their immature livers can't quite keep up.

The presence of enough bilirubin for the yellow pigment to be visible is called jaundice. Jaundice occurs in about 60% of healthy term infants and 80% of those born early. If the bilirubin concentration rises to about 5 mg/dL, the face takes on a yellow appearance. If the level reaches about 15 mg/dL, the yellow tint is visible from the head down to the midabdomen. At a level of 20 mg/dL, even the soles of the feet are yellow (note: these are approximations; a blood test is required to know the true bilirubin level).

Bilirubin is found throughout the body, not just in the skin. Under certain conditions, high concentrations of bilirubin are toxic to babies' brains. This is very rare when the concentration is under 25 mg/dL, but at higher concentrations, an increased risk for permanent hearing loss, mental retardation, spastic quadriplegia, or even death exists.

What might cause the bilirubin concentration to rise?

Anything that increases the number of expiring red blood cells soon after birth makes jaundice more likely. This might include the pounding babies take during difficult births (sometimes they look like little prizefighters) or the scalp hematomas caused by vacuum-assisted deliveries (one of my children looked like the ultimate conehead!). Perhaps the extra red blood cells applying for social security are the result of a blood-type incompatibility, delayed cord clamping, a congenital anemia, or an infection.

Anything that makes it tougher for the immature liver to process the bilirubin can also lead to jaundice, including prematurity, lack of oxygen, poor feeding, thyroid deficiency, a genetic enzyme deficiency, or a liver otherwise occupied with dealing with an infection.

Pitocin, a drug commonly used to induce delivery, is also associated with increased bilirubin levels.

The most common type of jaundice is called physiologic jaundice, the normal increased bilirubin in babies whose livers can't quite keep up with a slightly increased load of red blood cells.