Which factor contributes to the development of physiological jaundice in a newborn?

Jaundice is a yellow color to the skin and/or eyes caused by an increase in bilirubin in the bloodstream. Bilirubin is a yellow substance formed when hemoglobin (the part of red blood cells that carries oxygen) is broken down as part of the normal process of recycling old or damaged red blood cells. Bilirubin is carried in the bloodstream to the liver and processed so that it can be excreted out of the liver as part of bile (the digestive fluid produced by the liver). Bilirubin processing in the liver involves attaching it to another chemical substance in a process called conjugation.

• Processed bilirubin in the bile is thus called conjugated bilirubin.

• Unprocessed bilirubin is called unconjugated bilirubin.

Bile is transported through the bile ducts into the beginning of the small intestine (duodenum). If bilirubin cannot be processed and excreted by the liver and bile ducts quickly enough, it builds up in the blood (hyperbilirubinemia). As bilirubin levels in the blood increase, the whites of the eyes turn yellow first, followed by the skin. During the first week of life, the majority of full-term newborns develop unconjugated hyperbilirubinemia, often causing jaundice that normally resolves within a week or two (physiologic jaundice). Jaundice caused by unconjugated hyperbilirubinemia is even more common among premature infants.

Whether jaundice is dangerous depends on

• What causes the jaundice

• How high the bilirubin level is

• Whether the bilirubin is conjugated or unconjugated

Some disorders that cause jaundice are dangerous whatever the bilirubin level is. Extremely high unconjugated bilirubin levels regardless of cause are dangerous.

The most serious consequence of high unconjugated bilirubin levels is

• Kernicterus

Kernicterus is brain damage due to accumulation of bilirubin in the brain. The risk of this disorder is higher for newborns who are premature Preterm (Premature) Newborns A preterm newborn is a baby delivered before 37 weeks of gestation. Depending on when they are born, preterm newborns have underdeveloped organs, which may not be ready to function outside of... read more , who are seriously ill, or who are given certain drugs. If untreated, kernicterus may lead to significant brain injury resulting in developmental delay Definition of Developmental Disorders Developmental disorders are better called neurodevelopmental disorders. Neurodevelopmental disorders are neurologically based conditions that can interfere with the acquisition, retention, or... read more , cerebral palsy Cerebral Palsy (CP) Cerebral palsy refers to a group of symptoms that involve difficulty moving and muscle stiffness (spasticity). It results from brain malformations that occur before birth as the brain is developing... read more , hearing loss Hearing Impairment in Children Hearing impairment refers to any degree of hearing loss, mild to severe, and can occur when there is a problem with a part of the ear, including the inner, middle, and outer ears, or the nerves... read more

The most common causes of jaundice in the newborn are

• Physiologic jaundice (most common)

• Breastfeeding

• Excessive breakdown of red blood cells (hemolysis)

Physiologic jaundice occurs for two reasons. First, the red blood cells in newborns break down faster than in older infants resulting in increased bilirubin production. Second, the newborn's liver is immature and cannot process bilirubin and get it out of the body as well as in older infants. Almost all newborns have physiologic jaundice. It typically appears 2 to 3 days after birth (jaundice that appears in the first 24 hours after birth may be due to a serious disorder). Physiologic jaundice usually causes no other symptoms and resolves within 1 week. If the infant remains jaundiced at 2 weeks of age, doctors evaluate the infant for other causes of hyperbilirubinemia besides physiologic jaundice.

Breastfeeding can cause jaundice in two ways, which are called

• Breastfeeding jaundice (more common)

• Breast milk jaundice

Breastfeeding jaundice develops in the first few days of life and typically resolves in the first week. It occurs in newborns who do not consume enough breast milk, for example, when the mother's milk has not yet come in well. Such newborns have fewer bowel movements and thus eliminate less bilirubin. As newborns continue to breastfeed and consume more, the jaundice disappears on its own.

Breast milk jaundice differs from breastfeeding jaundice in that it occurs towards the end of the first week of life and may resolve by 2 weeks of age or persist for several months. Breast milk jaundice is caused by substances in breast milk that interfere with the liver getting rid of bilirubin from the body.

Excessive breakdown of red blood cells (hemolysis) can overwhelm the newborn's liver with more bilirubin than it can process. There are several causes of hemolysis, which are categorized by whether they are caused by an

• Immune disorder

• Nonimmune disorder

Less common causes of jaundice include

• Severe infections

• Certain hereditary disorders

• Obstruction of bile flow from the liver

Overwhelming bacterial infection (sepsis Sepsis in Newborns Sepsis is a serious bodywide reaction to infection spread through the blood. Newborns with sepsis appear generally ill—they are listless, do not feed well, often have a gray color, and may have... read more ) or urinary tract infection Urinary Tract Infection (UTI) in Children A urinary tract infection is a bacterial infection of the urinary bladder ( cystitis), the kidneys ( pyelonephritis), or both. Urinary tract infections are caused by bacteria. Infants and younger... read more without sepsis acquired during or shortly after birth can cause jaundice. Infections acquired by the fetus in the womb are sometimes the cause. Such infections include toxoplasmosis Toxoplasmosis Toxoplasmosis is infection caused by the single-celled protozoan parasite Toxoplasma gondii. Infection occurs when people unknowingly ingest toxoplasma cysts from cat feces or eat contaminated... read more and infections with cytomegalovirus Cytomegalovirus (CMV) Infection Cytomegalovirus infection is a common herpesvirus infection with a wide range of symptoms: from no symptoms to fever and fatigue (resembling infectious mononucleosis) to severe symptoms involving... read more or the herpes simplex Herpes Simplex Virus (HSV) Infections Herpes simplex virus infection causes recurring episodes of small, painful, fluid-filled blisters on the skin, mouth, lips (cold sores), eyes, or genitals. This very contagious viral infection... read more

Rubella Rubella is a contagious viral infection that typically causes mild symptoms, such as joint pain and a rash, but can cause severe birth defects if the mother becomes infected with rubella during... read more

While newborns are in the hospital, doctors periodically check them for jaundice. Jaundice is sometimes obvious in the color of the whites of the newborn's eyes or skin. But most doctors also measure the newborn's bilirubin level before discharge from the hospital. If the newborn has jaundice, doctors focus on determining whether it is physiologic and, if not, identifying its cause so that any dangerous causes can be treated. It is particularly important for infants to be evaluated for serious disorders if jaundice persists after 2 weeks of age.

In newborns with jaundice, the following symptoms are cause for concern:

• Jaundice that appears on the first day of life

• Jaundice in newborns over 2 weeks old

• Lethargy, poor feeding, irritability, and difficulty breathing

• A fever

Doctors are also concerned when bilirubin levels are very high or are increasing rapidly or when blood tests suggest that the flow of bile is reduced or blocked.

Newborns with warning signs should be evaluated by a doctor right away. If the newborn is discharged from the hospital on the first day after birth, a follow-up visit to measure the bilirubin level should done within 2 days of discharge.

Once at home, if parents notice that their newborn’s skin or eyes look yellow, they should contact their doctor immediately. The doctor can decide how urgently to evaluate the newborn based on whether the newborn has any symptoms or risk factors such as prematurity.

Doctors first ask questions about the newborn’s symptoms and medical history. Doctors then do a physical examination. What they find during the history and physical examination often suggests a cause and the tests that may need to be done.

During the physical examination, doctors check the newborn's skin to see how far jaundice has progressed down the body (the lower down on the body that jaundice is visible, the higher the bilirubin level). They also look for other clues suggesting a cause, particularly signs of infection, injury, thyroid disease, or problems with the pituitary gland.

Bilirubin levels are measured to confirm the diagnosis of jaundice, and tests are done to determine whether any elevated bilirubin is conjugated or unconjugated. Levels may be measured in a sample of blood or by using a sensor placed on the skin.

If the bilirubin level is high, other blood tests are done. They typically include

• Hematocrit (the percentage of red blood cells in blood)

• Examination of a blood sample under a microscope to look for signs of red blood cell breakdown

• Direct Coombs test (which checks for certain antibodies attached to red blood cells)

• Measurement of different types of bilirubin

• Blood type and Rh status (positive or negative) of the newborn and mother

Other tests may be done depending on results of the history and physical examination and on the newborn's bilirubin level. They may include culturing samples of blood, urine, or cerebrospinal fluid to check for sepsis, measuring levels of red blood cell enzymes to check for unusual causes of red blood cell breakdown, doing blood tests of thyroid and pituitary function, and doing tests for liver disease.

When a disorder is identified, it is treated if possible. High bilirubin levels themselves may also require treatment.

Physiologic jaundice usually does not require treatment and resolves within 1 week. For newborns being fed formula, frequent feedings can help prevent jaundice or reduce its severity. Frequent feedings increase the frequency of bowel movements and thus eliminate more bilirubin in stool. The type of formula does not seem to matter.

Breastfeeding jaundice may also be prevented or reduced by increasing the frequency of feedings. If the bilirubin level continues to increase, rarely, infants may need to be supplemented with formula.

In breast milk jaundice, mothers may be advised to stop breastfeeding for only 1 or 2 days and give their newborn formula and to express breast milk regularly during this break from breastfeeding to keep their milk supply up. Then they can resume breastfeeding as soon as the newborn's bilirubin level starts to decrease. While breastfeeding, mothers are usually advised not to give the newborn water or water containing sugar because doing so may decrease how much milk the newborn drinks and may disrupt the mother's milk production. However, breastfed infants who are dehydrated despite efforts to increase breastfeeding may need additional fluids.

High unconjugated bilirubin levels may be treated with

• Exposure to light (phototherapy)

• Exchange transfusion

This treatment is most commonly used, but it is not effective for all types of hyperbilirubinemia. For example, phototherapy is not used for infants with cholestasis. Phototherapy uses bright light to change bilirubin that has not been processed by the liver into a form that can be eliminated rapidly from the body by excretion in the urine. Blue light is the most effective, and most doctors use special commercial phototherapy units. Newborns are placed under the unit and undressed to expose as much skin as possible. They are turned frequently and left under the lights for variable periods of time (typically about 2 days to a week) depending on how much the bilirubin levels in the blood need to be lowered. Phototherapy can help prevent kernicterus. To determine how well the treatment is working, doctors periodically measure bilirubin levels in blood. Skin color is not a reliable guide.

This treatment is sometimes used when unconjugated bilirubin levels are very high and phototherapy is not sufficiently effective. An exchange transfusion can rapidly remove bilirubin from the bloodstream. A small amount of the newborn's blood is gradually removed (one syringe at a time) and replaced with (exchanged for) an equal volume of donor blood. The procedure usually takes about 2 hours. Exchange transfusion may also remove antibodies against red blood cells if the hyperbilirubinemia is due to blood type mismatch between mother and infant.

Exchange transfusions may need to be repeated if bilirubin levels remain high. Also, the procedure has risks and complications, such as heart and breathing problems, blood clots, and electrolyte imbalances in the blood.

The need for exchange transfusion has decreased since phototherapy has become so effective and since doctors have become better able to prevent problems resulting from incompatible blood types.

• In many newborns, jaundice develops 2 or 3 days after birth and disappears on its own within a week.

• Whether jaundice is of concern depends on what is causing it and how high the bilirubin levels are.

• Jaundice may result from serious disorders, such as incompatibility of the newborn’s and mother’s blood, excessive breakdown of red blood cells, or a severe infection.

• If jaundice develops in a newborn at home, parents should call their doctor right away.

• If jaundice is caused by a specific disorder, that disorder is treated.

• If high bilirubin levels require treatment, infants are typically treated with phototherapy and sometimes with exchange transfusions.

What causes physiologic jaundice in newborns?

Which factor contributes to the development of physiological jaundice in a newborn immature liver function?

What are common risk factors for developing newborn jaundice?

When do newborns get physiological jaundice?