Newborn Jaundice Risk Calculator
Estimate a newborn's jaundice risk score from bilirubin levels, postnatal age, gestational age, and clinical risk factors. Use this at the bedside or at home to decide whether a follow-up bilirubin check is warranted.
About this calculator
Neonatal jaundice occurs when total serum bilirubin (TSB) accumulates faster than the liver can conjugate and excrete it. Risk is not just about absolute bilirubin level — it depends on how old the baby is in hours, because TSB thresholds for concern rise with postnatal age. The formula normalizes bilirubin by postnatal age in days: adjustedBilirubin = bilirubin / (ageHours / 24 + 1). A prematurity multiplier of 1.2 is applied for gestational age < 37 weeks, because premature infants have less mature hepatic conjugation. A risk-factor multiplier (1.0 for low, 1.5 for medium, 2.0 for high) accounts for factors like G6PD deficiency, cephalohematoma, or bruising. A 10-point base is added for prematurity. The result is clamped between 0 and 100 as a risk score, not a clinical diagnosis.
How to use
Example: A 36-hour-old baby (ageHours = 36) born at 35 weeks (premature), TSB = 8 mg/dL, medium risk factors. Step 1: adjustedBilirubin = 8 / (36/24 + 1) = 8 / 2.5 = 3.2. Step 2: apply prematurity multiplier: 3.2 × 1.2 = 3.84. Step 3: apply medium risk multiplier: 3.84 × 1.5 = 5.76. Step 4: round to 6, then add 10 for prematurity = 16. Risk score = 16/100. A low score here reflects the relatively low absolute bilirubin, but the premature status means continued monitoring is still essential.
Frequently asked questions
What bilirubin level is dangerous for a newborn?
Danger thresholds depend heavily on the baby's age in hours and gestational age. For a full-term baby at 48 hours, most guidelines (AAP Bhutani nomogram) flag levels above 18 mg/dL as high risk; at 24 hours, even 12 mg/dL warrants urgent evaluation. Premature infants have lower thresholds — a 35-week baby may need phototherapy at levels that would be acceptable in a full-term newborn. This calculator provides a relative risk score, but clinical decisions must be made using validated nomograms and physician judgment.
What risk factors make newborn jaundice more serious?
Factors that accelerate bilirubin production or impair elimination significantly raise risk. Hemolytic conditions — ABO or Rh blood group incompatibility, G6PD deficiency, and hereditary spherocytosis — are among the most dangerous because they cause rapid bilirubin rise. Bruising from a difficult delivery or cephalohematoma adds extra bilirubin load as blood breaks down. Prematurity (< 37 weeks) reduces hepatic conjugation capacity. East Asian ethnicity and exclusive breastfeeding with poor latch and low intake are also recognized risk factors in AAP guidelines. Combinations of these factors compound the risk substantially.
When should I take my newborn to the doctor for jaundice?
You should seek same-day medical evaluation if your newborn appears yellow in the first 24 hours of life, or if yellow color spreads below the belly button or into the arms and legs. Other warning signs include extreme sleepiness (hard to wake for feeds), poor feeding, high-pitched cry, or arching of the back. The AAP recommends that all newborns be assessed for jaundice before hospital discharge and have a follow-up visit within 1–2 days if discharged before 72 hours of age. Do not rely solely on visual inspection — only a bilirubin blood test or transcutaneous meter gives an accurate level.