Phototherapy for neonatal jaundice decreases bilirubin by what percentage per hour?

• A. 10-20%
• B. 30-50%
• C. 60-70%
• D. 5-10%

Answer: (B)

Phototherapy lowers unconjugated bilirubin quickly by transforming it into water-soluble isomers that can be excreted without conjugation. When phototherapy is applied with high irradiance and broad skin exposure, the initial decline can be substantial—roughly one-third to one-half of the bilirubin level in the first hour. That’s why the 30-50% per hour range fits best among the options. The other percentages are less consistent with the typical rapid early response: too small (5-10% or 10-20% under intensive therapy) or unrealistically large (60-70% per hour). Real-world rate depends on factors like light intensity and wavelength, how much of the body is exposed, and the infant’s starting bilirubin level and overall hydration.