In physiological jaundice in term infants, serum bilirubin does not generally exceed:
**Core Concept**
Physiological jaundice in term infants is a common condition characterized by the elevation of serum bilirubin levels due to the breakdown of red blood cells and the immaturity of the liver's conjugation system. The bilirubin levels in these infants typically follow a predictable pattern, peaking in the first week of life.
**Why the Correct Answer is Right**
The serum bilirubin levels in physiological jaundice in term infants usually do not exceed 5 mg/dL (86 μmol/L) in the first 24 hours, 10 mg/dL (171 μmol/L) by 48 hours, and 15 mg/dL (257 μmol/L) by 72 hours of age. This is because the liver's conjugation system gradually matures, allowing it to efficiently process and excrete bilirubin. The levels then start to decrease, and by the end of the first week, they usually return to normal.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because bilirubin levels in physiological jaundice can exceed 5 mg/dL (86 μmol/L) in the first 24 hours, especially if the infant is premature or has other underlying conditions.
**Option B:** This option is incorrect because bilirubin levels in physiological jaundice can exceed 10 mg/dL (171 μmol/L) by 48 hours, especially if the infant has a high hemoglobin level or is not breastfed.
**Option C:** This option is incorrect because bilirubin levels in physiological jaundice can exceed 15 mg/dL (257 μmol/L) by 72 hours, especially if the infant has a high hemoglobin level or is not breastfed.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that physiological jaundice in term infants is usually benign and self-limiting, but it can be a sign of underlying conditions such as infection, congenital hypothyroidism, or hemolytic disease. A high bilirubin level or a bilirubin level that persists beyond the first week of life requires further investigation.
**Correct Answer:** C. 15 mg/dL (257 μmol/L).