Why does jaundice typically progress from head to toe in newborns?

• A. Unconjugated bilirubin is water soluble
• B. Unconjugated bilirubin is not absorbed
• C. Unconjugated bilirubin is fat soluble
• D. Unconjugated bilirubin is removed quickly

Answer: (C)

Jaundice in newborns progresses from head to toe due to the properties of unconjugated bilirubin, which is fat-soluble. When there's an excess of unconjugated bilirubin in the bloodstream—often due to the immature liver of newborns—it tends to deposit in tissues, particularly in those areas that are most vascular and have more fat content. Since unconjugated bilirubin is lipophilic, it more readily deposits in the skin and fatty tissues, beginning in the head and then moving downward as the concentration of bilirubin increases.

As jaundice develops, you will see its clinical manifestation starting from the facial region and progressing toward the lower parts of the body. This head-to-toe progression reflects the gravitational flow and distribution of bilirubin in tissues that have varying degrees of fat content and blood supply. In this context, understanding bilirubin's solubility and behavior in the body helps clarify why jaundice follows a specific pattern in newborns.