How are bilirubin levels used to guide phototherapy, and what nomograms help with this decision?

• A. Hour-specific bilirubin nomograms based on gestational age and weight guide phototherapy thresholds; phototherapy is started when levels cross the threshold.
• B. Bilirubin nomograms are based solely on postnatal age.
• C. Nomograms rely only on birth weight.
• D. Nomograms ignore hour-specific bilirubin levels.

Answer: (C)

Phototherapy decisions are guided by hour-specific bilirubin nomograms that are organized by how far along the infant is in hours of life and by gestational age. You plot the baby’s bilirubin level against their age in hours on the curve that matches their gestational age category. If the bilirubin value crosses the threshold line for that age and gestational age, phototherapy is indicated; if it’s below the line, careful observation is continued.

This approach reflects that risk changes as the infant gets older and that preterm or lower gestational-age infants have different threshold levels from term infants. It’s not based only on postnatal age or birth weight, and it requires looking at hour-specific bilirubin levels rather than a single value.