Figure 4: Guidelines for phototherapy in inpatient newborns at ≥ 35 weeks’ gestation. Use total serum bilirubin. Do not subtract direct reacting or conjugated bilirubin. The lines for lower, medium and higher risk refer to risk of neurotoxicity (for neurotoxicity risk factors, see Box 4). For well infants at 35 to 376/7 weeks’ gestation, total serum bilirubin levels can be adjusted for intervention around the medium risk line. It is an option to intervene at lower levels for infants closer to 35 weeks’ gestation and at higher levels for infants closer to 376/7 weeks’ gestation. Conventional phototherapy can be provided in hospital or at home at total serum bilirubin levels of 2–3 mg/dL (35–50 μmol/L) below those shown, but home phototherapy should not be used in any infant with risk factors. These guidelines refer to the use of intensive phototherapy, which should be used when the total serum bilirubin level exceeds the line indicated for each category. Infants are designated as higher risk because of the potential negative effects of the conditions listed on albumin binding of bilirubin, (41)– (43) the blood–brain barrier (44) and the susceptibility of the brain cells to damage by bilirubin. (44) Intensive phototherapy implies irradiance in the blue–green spectrum (wavelengths of about 430–490 nm) of at least 30 μW/cm2 per nanometre (measured at the infant’s skin directly below the centre of the phototherapy unit) and delivered to as much of the infant’s surface area as possible. Note that irradiance measured below the centre of the light source is much greater than that measured at the periphery. Measurements should be made with a radiometer specified by the manufacturer of the phototherapy system. If the total serum bilirubin level does not decrease or continues to rise in an infant who is receiving intensive phototherapy, this strongly suggests the presence of hemolysis. Reproduced with permission from Maisels et al., (5) Pediatrics 2009;124:1193–8. Copyright © 2009 American Academy of Pediatrics.