What Is Breastmilk Jaundice?

Jessica Madden

Jaundice is one of the most common newborn conditions, affecting 2 out of every 3 newborn babies. Babies with jaundice have yellow-looking skin from the buildup of a substance called bilirubin in their bodies that deposits in their skin. Doctors measure babies’ bilirubin levels through the skin, using a device called a transcutaneous bilirubinometer, or by doing special blood tests. Jaundice is diagnosed when an infant’s bilirubin level is greater than or equal to 5 mg/dL.

Bilirubin is produced when red blood cells are broken down. The liver metabolizes (breaks down) bilirubin into a form called conjugated bilirubin that enters into the intestines and leaves the body in stool. Babies are predisposed to jaundice for three main reasons: their red blood cells have shorter lifespans than adults, leading to a quicker turnover of red blood cells; their livers are not fully mature, so cannot conjugate bilirubin as efficiently as adults; and it’s not unusual for newborns to have delayed stooling during the first few days of life.

Breastfed infants are at a higher risk of jaundice than formula fed infants. Breastfeeding is associated with the development of two types of jaundice: breastfeeding jaundice and breastmilk jaundice. There is a lot of confusion about the differences between breastfeeding jaundice and breastmilk jaundice, even amongst medical professionals!

Breastfeeding jaundice is very common and occurs most often in exclusively breastfed infants in the first few days to week of life. It results from suboptimal breastmilk intake and is associated with dehydration, a decrease in urine and stool output, and ongoing weight loss. Having problems with breastfeeding, such as difficulty latching or a weak suck, puts babies at risk for this type of jaundice. Other names for breastfeeding jaundice include “breastfeeding-associated jaundice,” “breast-non-feeding jaundice,” and “starvation jaundice.” The Academy of Breastfeeding Medicine (ABM) recommends that this type of jaundice be called “suboptimal intake jaundice.” Breastfeeding jaundice should not last more than two weeks and resolves once a newborn is getting enough milk and no longer losing weight.

Breastmilk jaundice, which starts later than breastfeeding jaundice, occurs in healthy, full-term breastfed babies who are feeding well, not losing weight, and have mothers with good breastmilk supplies. It’s estimated that up to 30-40% of exclusively breastfed infants in the U.S. have some degree of breastmilk jaundice during the first 3 weeks of life, with bilirubin levels greater than or equal to 5 mg/dL, and that between 2-4% of breastfed babies have levels greater than 10 mg/dL. Babies with breastmilk jaundice have higher peak bilirubin levels and slower declines than what is seen in other types of newborn jaundice. Babies with breastmilk jaundice can have elevated bilirubin levels, with levels as high as 18 mg/dL, for up to 8-12 weeks.

Breastmilk jaundice is a “diagnosis of exclusion,” which means that all other causes of newborn jaundice must be ruled out before it can be diagnosed. A newborn cannot be diagnosed with breastmilk jaundice if their elevated bilirubin levels are due to any other cause, such as prematurity, blood group incompatibility (i.e. ABO incompatibility or Rh disease), G6PD deficiency, and other hereditary and genetic causes (i.e. hereditary spherocytosis or elliptocytosis). The blood tests that are most often used in newborn babies’ jaundice evaluations include indirect and direct bilirubin levels, complete blood cell counts, reticulocyte counts, and peripheral blood smears.  Babies who have breastfeeding jaundice can develop breastmilk jaundice; but in these cases they cannot be diagnosed with breastmilk jaundice until they have good milk intake, healthy weight gain, and no signs of dehydration – this is usually when they are at least a few weeks old and any breastfeeding problems have resolved.

Breastmilk jaundice runs in families and occurs equally in boy and girl infants. We do not have a good understanding of why breastmilk jaundice occurs. Current hypotheses include: certain babies may have a genetic susceptibility to developing breastmilk jaundice, it might result from an imbalance in newborns’ gut flora, and/or there might be a substance in some mothers’ breastmilk that prevents babies’ livers from breaking down bilirubin efficiently, causing it to build up.

UDP-glucuronosyltransferase (UGT) is an enzyme that is necessary for bilirubin metabolism, or breakdown. The UGT1A1 gene gives our bodies instructions to make UGT. All newborn babies have lower activity levels of UGT at baseline, and mutations in the UGT1A1 gene create variants of UGT that are even less effective at breaking down and metabolizing bilirubin.  Thus, babies who have UGT1A1 gene mutations are genetically predisposed to getting breastmilk jaundice.

The bacterial microflora of the intestines appears to play an important role in the metabolism of bilirubin in the newborn gut. It’s hypothesized that an overgrowth of “bad” gut bacteria decreases UGT1A1 gene activity, leading to lower levels of UGT and a buildup of bilirubin in the intestines. Bilirubin then recirculates into the bloodstream, via a process called enterohepatic circulation, and causes jaundice. Some other bacteria produce an enzyme called B-glucuronidase which stimulates enterohepatic circulation of bilirubin from the intestinal tract back to the blood. Changes in the activity levels of both the UGT and B-glucuronidase enzymes shift bilirubin out of the stool, where it is supposed to leave the body, and back into the bloodstream, where it deposits into the skin, mucous membranes, etc. and causes jaundice.

The bacteria present in breastmilk colonizes babies’ intestines.  Recent research has shown a link between the presence or absence of certain types of bacteria in both mothers’ milk and babies’ intestines and the development of breastmilk jaundice. The mothers’ milk of infants with breastmilk jaundice appears to have higher levels of Streptococcus and lower levels of Bifidobacterium than the breastmilk of mothers whose babies do not develop jaundice. Additionally, the stools of babies with breastmilk jaundice have been found to have higher levels of Proteobacteria and E. coli, and lower levels of Bifidobacterium than babies who do not develop breastmilk jaundice. Future research will need to determine if giving newborns probiotics, such as those that contain Bifidobacterium, decreases the risk of the development of breastmilk jaundice.

In addition to differences in bacterial species, all the following differences have been found in the breastmilk from mothers of newborns with breastmilk jaundice:

  • higher levels of cytokines
  • higher cholesterol levels
  • lower levels of epidermal growth factor
  • increased bile salts

It’s unclear if these findings are all inter-related and/or if they actually cause breastmilk jaundice. The bottom line is that we need more research to understand why breastmilk jaundice occurs, what the main triggers for this type of jaundice are, and what we can do to try to prevent it from occurring.

In most cases, breastmilk jaundice resolves on its own without treatment and has an excellent prognosis. However, in all cases of breastmilk jaundice, close monitoring of bilirubin levels is important to prevent kernicterus. Kernicterus is a type of brain damage that occurs in the setting of very high bilirubin levels, leading to bilirubin deposits in the brain. The American Academy of Pediatrics (AAP) has detailed guidelines as to when to treat jaundice so that kernicterus can be prevented.

The main treatment for breastmilk jaundice is phototherapy, which is prescribed by doctors per the AAP’s guidelines. Phototherapy converts bilirubin into an isomer that is easily excreted by the body. Mild cases of jaundice that require phototherapy can be treated in the home setting, but more serious cases usually require admission to the hospital for intensive phototherapy. It used to be recommended that moms of babies with breastmilk jaundice stop breastfeeding for 24-48 hours to see if their babies’ bilirubin levels would come down when receiving infant formula. This is no longer the standard of care and stopping breastfeeding should only be done in very severe cases of breastmilk jaundice with bilirubin levels that do not decrease with phototherapy. If breastfeeding does need to be interrupted, it’s extremely important that mothers get the support they need to pump to maintain their breast milk supplies.

In conclusion, breastmilk jaundice is common, occurs in healthy breastfeeding newborns, and usually resolves on its own. If you are breastfeeding and your baby develops jaundice, please know this is not your “fault,” there is nothing wrong with your breastmilk, and you should not feel like you must stop breastfeeding. Even if your baby needs to have phototherapy, I can assure you that he or she will be okay!


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