Yellow Baby: Normal or Problem?
Physiologic jaundice peaks at day 3-5 in a term kid, day 5-7 in preterm. It's just the immature liver not conjugating fast enough, plus the shortened RBC lifespan and poor feeding intake pushing bilirubin back into circulation. Self-limited, usually.
Pathologic jaundice presents differently: it appears in the first 24 hours, rises more rapidly than expected, or persists beyond 3-4 weeks. This may indicate hemolytic disease (ABO/Rh incompatibility, G6PD deficiency), sepsis, cholestasis, or other serious etiologies, and requires thorough investigation.
The 2022 AAP update revised phototherapy thresholds based on gestational age and neurotoxicity risk factors. For low-risk term infants, thresholds were raised (resulting in less phototherapy), while for preterm infants and those with neurotoxicity risk factors, thresholds were lowered (more aggressive treatment).
The Bhutani Nomogram
A bilirubin of 15 mg/dL at 48 hours is totally different from 15 mg/dL at 96 hours, that's what the Bhutani nomogram captures. Plot the TSB against hours of life and you get your risk zone.
The Bhutani Nomogram calculator does this, but know what it's doing: it's stratifying by the baby's age in hours, gestational age, and risk factors (hemolytic disease, asphyxia, sepsis, etc.). A 30-weeker sits at much lower thresholds than a 39-weeker because the preterm brain is more vulnerable to bilirubin neurotoxicity at the same TSB level.
Phototherapy Thresholds
The AAP Bilirubin 2022 calculator reflects the 2022 update. Key changes include explicit incorporation of neurotoxicity risk factors (isoimmune hemolytic disease, G6PD deficiency, gestational age 35–37 weeks, albumin <3.0 g/dL, sepsis, or significant clinical instability), updated hour-specific thresholds, and clearer guidance on when to escalate to exchange transfusion.
Intensive phototherapy (spectral irradiance ≥30 μW/cm²/nm using blue LED lights at 460–490 nm wavelength) reduces bilirubin faster than conventional phototherapy. If TSB is rising rapidly or approaching exchange transfusion thresholds, use intensive phototherapy with maximal skin surface exposure.
Check bilirubin every 12-24 hours once you start phototherapy, sooner if it's climbing fast. Document when you started, what type of lights you used, and the kid's risk category.
Bilirubin-Albumin Ratio
The B/A ratio estimates how much bilirubin is free and unbound, the stuff that can cross the blood-brain barrier and cause kernicterus. TSB alone doesn't tell you this. A baby with low albumin or conditions that impair albumin binding (sepsis, acidosis, low temperature) is at higher neurotoxicity risk for the same TSB.
In hemolytic disease, this ratio is particularly important. Rapid hemolysis produces high TSB quickly. The Bilirubin-Albumin Ratio calculator helps determine whether exchange transfusion is indicated before the TSB threshold alone would suggest intervention.
Exchange Transfusion
Exchange transfusion is reserved for severe hyperbilirubinemia. Thresholds are substantially higher than phototherapy thresholds; exchange is not performed until the infant is at genuine risk for bilirubin neurotoxicity. A low-risk term infant might require phototherapy at TSB 18 mg/dL but would not require exchange until 25-26 mg/dL. Use the Exchange Transfusion calculator to check the appropriate threshold.
Indications for exchange transfusion include failure of phototherapy to control rising TSB, bilirubin rising faster than 0.2 mg/dL/hour, or signs of bilirubin encephalopathy such as irritability, poor feeding, high-pitched cry, or hypertonia.
Kernicterus is now uncommon but remains permanent. Missed diagnosis or delayed treatment can result in permanent neurologic sequelae affecting the child's lifelong development.
Risk Categories
The 2022 AAP guidelines stratify risk by gestational age and the presence of neurotoxicity risk factors (isoimmune hemolytic disease, G6PD deficiency, albumin <3.0 g/dL, sepsis, or significant clinical instability):
Higher risk: Gestational age 35–37 weeks with neurotoxicity risk factors. These infants have the lowest phototherapy thresholds.
Medium risk: Gestational age 35–37 weeks without risk factors, or ≥38 weeks with neurotoxicity risk factors.
Lower risk: ≥38 weeks, healthy, feeding well, no neurotoxicity risk factors. These infants have the highest phototherapy thresholds.
As an example, a healthy term infant at 48 hours of age may have a phototherapy threshold of approximately 18 mg/dL, while a late preterm infant with hemolytic disease at the same age may have a threshold of approximately 12–13 mg/dL.
Getting Them Home
Check bilirubin before discharge, either TSB or transcutaneous. Use the nomogram to see where they sit.
If they go home on phototherapy, make sure the family understands feeding (frequent and well), hydration, and proper light positioning. Arrange a follow-up TSB check within 24 hours.
Watch for rebound bilirubin after you stop phototherapy, about 10-15% of babies rebound. If they had hemolytic disease or were feeding poorly, be extra cautious and check them sooner.