5.1 Jaundice and Hyperbilirubinemia

Bilirubin Metabolism: Why Newborns Turn Yellow

Jaundice is yellow discoloration of skin and sclera caused by elevated bilirubin in the blood (hyperbilirubinemia). Roughly 60-80% of healthy term and late-preterm newborns show some visible jaundice, so the IBCLC must understand it cold. Bilirubin is a breakdown product of heme from red blood cells. Newborns produce bilirubin rapidly because they are born with a high red-cell mass and those cells have a shorter lifespan than adult cells.

The newly produced bilirubin is unconjugated (fat-soluble, bound to albumin). The infant liver must conjugate it with glucuronic acid (via the enzyme UGT1A1) to make it water-soluble so it can be excreted in bile into the gut and removed in stool.

Two newborn realities slow this down: the liver enzyme system is immature, and an enzyme in the newborn gut (beta-glucuronidase) can deconjugate bilirubin so it is reabsorbed back into the blood. This reabsorption loop is called the enterohepatic circulation, and it is the single mechanism the IBCLC can most influence — because moving milk through the gut means moving bilirubin out in stool.

Physiologic vs. Pathologic Jaundice

Physiologic jaundice is benign and expected. It appears after the first 24 hours of life, peaks around day 3-5 (sometimes to day 7 in East Asian infants), and resolves within about two weeks in term infants. It simply reflects normal red-cell breakdown plus an immature liver.

Pathologic jaundice is the exam's most reliable red flag: any jaundice appearing within the first 24 hours of life is abnormal until proven otherwise and requires immediate medical evaluation. Other warning features include a rapid rise in bilirubin, a very high total level, jaundice extending below the chest, or jaundice that persists or worsens beyond the expected window. Pathologic causes include hemolysis (ABO or Rh incompatibility, G6PD deficiency), sepsis, cephalohematoma, and biliary obstruction — none of which the IBCLC treats, but all of which the IBCLC must recognize as triggers to refer.

The Two Breastfeeding-Related Patterns

Learn these as a contrasting pair — they are timed and managed differently, and the exam loves to test the distinction.

Breastfeeding jaundice — better termed suboptimal-intake jaundice — is early-onset, usually in the first week. It is caused by insufficient milk intake: too few effective feeds means too little stooling, so bilirubin sitting in the gut is reabsorbed through increased enterohepatic circulation. It is fundamentally a feeding problem dressed up as a liver problem, and the remedy is more frequent, effective breastfeeding, not stopping the breast.

Breast-milk jaundice is later-onset, typically appearing after day 4-7 and sometimes persisting for weeks. Factors in mature milk are thought to increase intestinal bilirubin reabsorption. The key clinical clue is that the infant is otherwise thriving — gaining weight, ample diapers — so breastfeeding is normally continued while the provider monitors bilirubin.

How Feeding Clears Bilirubin, and When to Refer

The single most important lactation intervention for early jaundice is frequent, effective feeding — about 8-12 feeds per 24 hours. Colostrum has a laxative effect; moving milk through the gut promotes stooling, which carries bilirubin out and reduces enterohepatic reabsorption. The IBCLC's management list:

1. Assess the feed — latch, audible swallowing, milk transfer, output (wet and stooling diapers).
2. Increase frequency and effectiveness — wake a sleepy infant, use breast compression, ensure deep latch.
3. Protect supply — add hand expression or pumping if transfer is poor, and feed expressed milk.
4. Track output and weight as objective markers of intake.
5. Refer for bilirubin measurement (transcutaneous or serum) per the triggers below.
6. Reinforce, do not replace, the medical plan.

Refer whenever jaundice appears in the first 24 hours, spreads below the chest/abdomen, or comes with poor feeding, lethargy, or excess weight loss. Under the 2022 AAP hyperbilirubinemia guideline (infants ≥35 weeks), the provider no longer uses a single hour-specific nomogram; instead, treatment thresholds are set by gestational age plus neurotoxicity risk factors along a continuum. Breastfeeding is generally continued during phototherapy — interrupting the breast is rarely necessary, and abrupt weaning is never the IBCLC's recommendation. The lactation role is to keep milk moving, protect supply, and support the dyad.

Worked Example: A 3-day-old is brought in for visible jaundice to the chest. History: latches only 4-5 times per day, mother reports "he sleeps through feeds," birth weight 3,400 g, today 3,060 g (10% loss), only one small stool in 24 hours. The IBCLC recognizes an early suboptimal-intake jaundice pattern: underfeeding → few stools → bilirubin reabsorbed via enterohepatic circulation. Plan: wake and feed every 2-3 hours (target 8-12/day), correct the shallow latch, add breast compressions, begin hand-expression of colostrum to feed any infant who will not transfer, and refer same-day for a bilirubin level because the jaundice has spread below the chest with excess weight loss. The IBCLC does NOT advise stopping the breast — that would worsen the underlying intake problem.