OVERVIEW

What is breast milk jaundice?

Breast milk jaundice refers to the persistence of benign neonatal hyperbilirubinemia (i.e., physiological jaundice) beyond the first week of life. It typically occurs in exclusively or predominantly breastfed newborns, appearing 3–5 days after birth, peaking around 2 weeks, and gradually declining to normal levels over the next 3–12 weeks (if breastfeeding continues). If breastfeeding is discontinued, jaundice usually subsides significantly within 48–72 hours. The newborn exhibits normal growth and development, and other causes of non-physiological hyperbilirubinemia can be ruled out.

Depending on bilirubin levels, management may include continuing breastfeeding, temporarily stopping breastfeeding, or phototherapy intervention. No other treatments—such as sun exposure, probiotics, or jaundice-reducing medications—are necessary. Breast milk jaundice has a favorable prognosis and does not affect routine vaccinations if the infant is otherwise healthy with no complications.

SYMPTOMS

What are the symptoms of breast milk jaundice?

Breast milk jaundice is a special type of neonatal jaundice associated with breastfeeding. Bilirubin deposits in the skin, mucous membranes, and subcutaneous tissues, causing them to turn yellow. The main manifestation is "jaundice," characterized by yellowing of the skin and sclera.

Can breast milk jaundice cause acute bilirubin encephalopathy?

Acute bilirubin encephalopathy caused solely by breast milk jaundice is extremely rare. Abnormal elevation of jaundice is often due to other underlying causes or a combination of factors. Regardless, jaundice should be monitored in the first 5 days after birth, and follow-up should be conducted as advised by a doctor. Prompt management of hyperbilirubinemia is essential to reduce the risk of acute bilirubin encephalopathy.

Bilirubin is a potential neurotoxin, and the risk of acute bilirubin encephalopathy increases with severe jaundice. Breast milk jaundice rarely exceeds 20 mg/dl (342 μmol/L). However, when total bilirubin levels reach or exceed 25 mg/dl (428 μmol/L), healthy full-term infants are at risk of neurological dysfunction. With active intervention, acute bilirubin encephalopathy caused by abnormally high jaundice may be reversible, but it can also lead to permanent, irreversible neurological damage (kernicterus).

How is neonatal jaundice classified by severity?

• Based on the level of serum total bilirubin (TSB), it can be categorized as:

• Severe hyperbilirubinemia: Peak TSB > 342 μmol/L (20 mg/dl);

• Extremely severe hyperbilirubinemia: TSB > 427 μmol/L (25 mg/dl);

• Dangerous hyperbilirubinemia: TSB > 510 μmol/L (30 mg/dl). All other cases are classified as mild or moderate.

CAUSES

What causes breast milk jaundice?

The mechanism of "breast milk jaundice" is not yet fully understood. It may be related to the following reasons:

• Breast milk contains high concentrations of β-glucuronidase, which catalyzes the hydrolysis of β-D-glucuronic acid. A reduction in β-D-glucuronic acid can promote increased intestinal absorption of unconjugated bilirubin. Infant formula contains very low levels of β-glucuronidase, so formula-fed infants have lower bilirubin levels than breastfed infants.

Some studies suggest that β-glucuronidase inhibitors, such as enzymatically hydrolyzed casein or L-aspartic acid found in casein hydrolysate formula, may help prevent breast milk jaundice. However, although breast milk jaundice lasts longer, it has almost no adverse effects, so using special formulas (containing β-glucuronidase inhibitors) appears to offer no benefit. Therefore, the use of such products for treating breast milk jaundice is not recommended.

• Another possible mechanism is the polymorphic mutation of the UGT1A1 gene. A Japanese study involving 170 newborns with breast milk jaundice found that half of the infants were homozygous for the UGT1A1*6 genotype, and these homozygous infants had higher jaundice levels than those with other genetic polymorphisms.

In contrast, the control group of infants did not carry the UGT1A1*6 genotype. However, further research in other regions of the world is needed to determine whether there is a causal relationship between genetic variations in the UGT1A1 gene and breast milk jaundice. Therefore, routine genetic testing is currently not recommended for evaluating breast milk-associated jaundice.

DIAGNOSIS

How is breast milk jaundice diagnosed?

For newborns who are exclusively or primarily breastfed, if jaundice continues to rise or persists at a hyperbilirubinemia level 1–2 weeks after birth, but significantly subsides within 48–72 hours after stopping breastfeeding, and the newborn shows good growth and development without other abnormalities or discomfort, a clinical diagnosis of breast milk jaundice can be made.

What conditions should breast milk jaundice be differentiated from?

If the rise and fall of jaundice do not match the characteristics of breast milk jaundice, other causes or pathological factors leading to jaundice should be considered.

It should also be distinguished from "breastfeeding jaundice": In the first 3–5 days of life, exclusively breastfed newborns may have higher bilirubin levels than formula-fed newborns due to insufficient breast milk intake and delayed meconium passage, increasing enterohepatic circulation. In some cases, bilirubin may even reach levels requiring intervention. There are also instances where inadequate feeding persists beyond the first week, with symptoms such as reduced urine output (yellow or brick-red), decreased stool frequency, physiological weight loss >12%, and poor subsequent weight gain.

Management of breastfeeding jaundice mainly involves helping mothers establish successful breastfeeding to ensure adequate milk intake, with formula supplementation if necessary. Jaundice management can refer to the intervention criteria for breast milk jaundice and neonatal jaundice.

TREATMENT

Which department should I visit for breast milk jaundice?

Neonatology, pediatrics, and child healthcare departments are all suitable.

How is breast milk jaundice treated?

After clinical diagnosis of breast milk jaundice:

• When serum total bilirubin (or transcutaneous measurement) is <257 μmol/L (15 mg/dl), breastfeeding does not need to be stopped.

• When serum total bilirubin (or transcutaneous measurement) is >257 μmol/L (15 mg/dl), breastfeeding may be paused for 3 days and replaced with formula feeding. Blood tests may also be considered to check total bilirubin, liver function, etc. After stopping breastfeeding for 3 days, bilirubin levels typically drop to 120–154 μmol/L (7–9 mg/dl), at which point breastfeeding can resume with regular monitoring of bilirubin levels. This cycle of stopping and resuming breastfeeding can be repeated.

• When serum total bilirubin (blood test required) is >342 μmol/L (20 mg/dl), phototherapy is administered to reduce bilirubin.

Can babies with breast milk jaundice be exposed to sunlight?

Babies with breast milk jaundice can engage in regular outdoor activities. Although direct sunlight exposure has been shown to reduce bilirubin levels, it is not recommended as a treatment to prevent severe hyperbilirubinemia due to the risk of sunburn from direct exposure of uncovered skin.

Additionally, infants exposed to direct sunlight may also be subjected to unnecessary and potentially harmful ultraviolet radiation, increasing the risk of skin malignancies.

Can oral medications be used for breast milk jaundice?

When phototherapy is required, medications are not particularly helpful. When phototherapy is unnecessary, medications are also not needed. Therefore, following the phototherapy protocol is sufficient, and no oral medications claiming to reduce jaundice—including probiotics, herbal medicines, or chemical drugs like phenobarbital—are required.

DIET & LIFESTYLE

Does breast milk jaundice require dietary restrictions?

No, breastfeeding mothers can maintain a normal diet with balanced nutrition.

Can babies with breast milk jaundice receive vaccinations?

If the infant with breast milk jaundice is in good general condition without other complications, it does not affect routine vaccinations.

PREVENTION

Can breast milk jaundice be prevented?

If breastfeeding is provided, it cannot be prevented.

Can bilirubin encephalopathy be prevented?

Prevention of bilirubin encephalopathy primarily involves actively reducing bilirubin levels while minimizing high-risk factors:

• Conduct prenatal check-ups to prevent premature birth and difficult delivery as much as possible;

• Avoid the misuse of medications such as vitamin K and sulfonamides during the perinatal period;

• Closely monitor jaundice in newborns within 72 hours after birth and intervene promptly if intervention criteria are met;

• Diagnose and treat neonatal hemolytic disease early;

• Promptly correct conditions such as asphyxia, hypoglycemia, acidosis, and infections.