Physiologic Jaundice of the Newborn

newborn with jaundiced face

Jaundice is a condition in which patients have a yellowish skin color. It is a very common occurrence in newborn babies, and it is due to increased levels of the chemical called bilirubin. Hence, physiologic jaundice is also called physiologic hyperbilirubinemia or physiologic bilirubinemia.

Approximately 60%-70% of newborn babies have some degree of jaundice during the first week of life after birth. The majority of newborns have only physiologic jaundice. Adjective “Physiologic” is added to signify that even though bilirubin levels are increased, they are at safe levels and do not need to be treated. Also, “physiologic” means that the baby does not have any reasons for jaundice other than being a newborn.

If the baby has additional pathologic processes contributing to its jaundice, the condition will be called “Pathologic Jaundice.”I wrote an exhaustive article focused on the topic of Jaundice that you can access as well.

The following conditions are some examples of pathologic jaundice:

  • Immune hemolytic jaundice (more about it in my article)
  • Jaundice due to infections
  • Jaundice due to hematomas or trauma
  • Jaundice due to breastfeeding or breast milk composition
  • Jaundice due to enzymatic defects in red blood cells (G6PD)
  • Jaundice due to genetic abnormalities
  • Jaundice due to endocrine abnormalities (Hypothyroidism)
  • Jaundice due to metabolic defects (GAlactosemia)

Causes of physiologic jaundice in a newborn.

Three physiologic mechanisms occur in a newborn after birth and cause physiologic jaundice:

  • Increased production of bilirubin
  • Impaired elimination of bilirubin from the body
  • Increased reabsorption of bilirubin from the gut back into circulation

Increased production of bilirubin

Bilirubin is a byproduct of the break down of red blood cells and occurs naturally in our bodies. Red cells have a limited life span and continuously undergo destruction, while bone marrow keeps producing new red cells. Newborn babies have a much higher initial number of red cells, and their red cells have a shorter life span than in adults. Thus they produce more bilirubin after birth.

Impaired elimination of bilirubin from the body of the newborn

Bilirubin must undergo a chemical transformation before being excreted from the body. The liver enzymes facilitate these necessary chemical reactions. Unfortunately, all newborns, including full-term newborns, are born with an inadequate amount of liver enzymes participating in the transformation of the bilirubin. After several weeks, the liver enzymes in newborns achieve comparable activity to the one in adults.

Increased reabsorption of bilirubin from the gut back into the circulation

Right after birth, newborn babies do not eat a lot. Mothers who breastfeed don’t usually have much breast milk in the first few days after delivery. Suboptimal oral intake contributes to contents in the bowel loops moving rather slowly, and that, in turn, results in reabsorption of excreted bilirubin back into the circulation.

Once the baby establishes good feeding patterns and has regular stools, bilirubin reabsorption from the gut decreases significantly.

Physiologic jaundice versus pathologic jaundice in a newborn

Doctors make a diagnosis of physiologic jaundice by excluding all other possibilities first. It isn’t straightforward to predict if the baby with jaundice has a physiologic disease or pathologic hyperbilirubinemia.

To make a final determination, we need to exclude the most common forms of pathologic jaundice and know what the peak bilirubin level is going to be.

If a baby has jaundice with additional risk factors for hyperbilirubinemia (blood type incompatibility, bruising, weight loss, infections, prematurity, or others), the diagnosis is going to be pathologic jaundice.

Also, if the baby does not have risk factors for jaundice, but bilirubin levels are abnormally high requiring phototherapy, jaundice disease can not be called physiologic jaundice any more. In such a scenario, some doctors will call it “exaggerated physiologic jaundice” while others “pathologic jaundice.”

Visual assessment of the baby’s skin color should not be used to assess the severity of newborn jaundice. There are two reasonably objective methods allowing us to do that. The transcutaneous technique is performed by placing an apparatus on the baby’s skin and getting a readout; it is none-invasive and quick. The blood test for bilirubin levels is more accurate, gives us much more information, but requires a blood draw and obviously is less comfortable for the baby.

Treatment of a physiologic jaundice

Physiologic jaundice does not require treatment. By definition, “physiologic” should mean healthy and safe. However, when the baby has jaundice disease with bilirubin levels necessitating treatment, and we can’t find reasons for that pathologic jaundice, sometimes we use the term “exaggerated physiologic jaundice.”

As doctors, we should be careful while using this term, so we do not confuse others and do not get a false sense of security that we have the final diagnosis. It is always possible that when using the term “exaggerated physiologic jaundice, we just can’t find the right diagnosis.

Phototherapy (light therapy) is the first line of treatment in all types of typical newborn jaundice. I wrote a whole article on Phototherapy. I described indications for the phototherapy, mechanism of action, and side effects associated with the therapy. Bilirubin levels at which phototherapy is indicated vary and depend on: age of the baby, gestational age, and presence of additional risk factors for jaundice (Source).

Phototherapy works by changing bilirubin into a water-soluble form facilitating its excretion from the body. It is benign and harmless therapy for the vast majority of babies. The most commonly cited adverse effects associated with phototherapy are dehydration, fever, skin rashes, and separation from the mother during therapy.

Prognosis in physiologic jaundice

If jaundice is truly physiologic, bilirubin returns to adult levels within 1-2 weeks after birth. However, every newborn baby needs to be monitored very carefully to ensure that the baby does not need phototherapy treatment or bilirubin levels are not dangerously high.

White American and African American babies reach peak bilirubin levels of 5-6 mg/dl during the first week of life. Asian American newborns reach peak bilirubin of 10-14 mg/dl. Those values will be considered normal or physiologic for these populations provided they did not occur within the first 48 hours after birth.

During the first day of life, bilirubin values that can be considered normal are much lower than the above-mentioned peak values.

Is physiologic jaundice of the newborn dangerous?

Physiologic jaundice is not dangerous. However, pathologic jaundice may be hazardous. In pathologic jaundice, bilirubin levels may reach dangerous levels for the baby’s brain, causing Acute Encephalopathy and subsequently Chronic Bilirubin Induced Neurologic Deficiencies (Source).

Severe neurological damage may result in cerebral palsy, cognitive impairment, or even death. But, again, I want to emphasize, all those consequences are not due to physiologic jaundice, they can occur in pathologic hyperbilirubinemia. (More on this subject read here).

How can I help my baby resolve physiologic jaundice?

You can make sure that your baby eats regularly and is well hydrated. Proper nutrition and regular bowel movements will affect the faster passage of bowel contents and influence decreased bilirubin reabsorption from the gut, thus reducing total bilirubin load in the circulation.

You may also like to read my other more comprehensive article on the topic of Jaundice that covers pathologic jaundice, causes of jaundice, treatments, and complications


This article is only for general information purposes. It should not be viewed as any medical advice. There is a chance that information here may be inaccurate. It would be best if you always discussed all health-related matters with your doctor before making any decisions that may affect your health or health of your family members.


Dr.Wisniewski is a board-certified pediatrician and neonatologist with over 20 years of clinical experience in the USA. He authored the book: "Babies Born Early - A guide for Parents of Babies Born Before 32 Weeks" Dr.Wisniewski loves educating parents on various health conditions affecting their newborn babies and children.

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