In plain words
UGT1A1 is a gene that makes an enzyme in the liver. The enzyme changes , the yellow pigment from old red blood cells, into a form the body can clear. A newborn's liver is still learning to do this, so bilirubin can build up for a few days. Some families carry versions of this gene that work more slowly. Those versions are linked to more noticeable in newborns and to a type called . Testing is not routine. Your pediatrician will look at the bilirubin level and the baby's age to decide what happens next.
The deeper version
UGT1A1 encodes bilirubin uridine diphosphate glucuronosyltransferase, the sole hepatic enzyme conjugating unconjugated bilirubin. Promoter polymorphisms reduce transcription: the TA7 repeat (UGT1A1*28) is common in European populations and the G71R variant (UGT1A1*6) in East Asian populations, both reducing enzyme activity. These variants are associated with prolonged neonatal jaundice and breast milk jaundice, with Maruo and colleagues (2000) reporting that variants in the UGT1A1 gene were linked to prolonged breast milk jaundice in Japanese infants. Clinical genotyping is not recommended for routine care, and the AAP's 2022 guideline uses bilirubin level and gestational age for management.
Where it comes up
- Newborn jaundiceBaby Basics
- Feeding a baby with jaundiceFeeding Your Baby
- Newborn weight: the early drop and regainingBaby Basics
- Dairy and other sensitivities in a breastfed babyFeeding Your Baby
What mothers here say about UGT1A1
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Sources
- American Academy of Pediatrics — Clinical Practice Guideline Revision: Management of Hyperbilirubinemia in the Newborn Infant 35 or More Weeks of Gestation, 2022
- Maruo Y et al. — Prolonged unconjugated hyperbilirubinemia associated with breast milk and mutations of the bilirubin uridine diphosphate-glucuronosyltransferase gene. Pediatrics 2000