Bilirubin levels in newborns
Bilirubin levels can cause concern for parents whose newborns are suspected to have jaundice. It’s estimated that 60% of full term and 80% of premature babies develop jaundice (hyperbilirubinaemia) in the first week after birth.
What is bilirubin?
Bilirubin is a yellow substance, which is a byproduct of red blood cells being broken down. Jaundice occurs when bilirubin is not excreted from the body fast enough and builds up.
In most cases, jaundice is harmless. It usually appears some time in the first week after birth, and disappears without treatment after a few weeks.
A few babies can become severely jaundiced, and need investigation and treatment to prevent possible serious complications from developing.
Three types of jaundice seen in newborns
To understand newborn jaundice, firstly, it’s important to know there are different forms of jaundice.
Here are three types of jaundice seen in newborns:
- Physiologic Jaundice: occurs due to high concentration of red blood cells and immature liver function, usually appears 2-4 days after birth and resolves in 1-2 weeks (3 weeks if premature). It is not associated with underlying disease or disorders.
- Pathological jaundice: is always considered if jaundice develops in the first 24 hours after birth, or if levels are very high from 24 hours to 10 days of age, or the baby shows signs of serious illness.
- Breast milk jaundice (also known as breastfeeding jaundice): occurs 5-7 days after birth, typically peaks at 14 days and can last as long as a few months. It’s thought to be caused by an increased concentration of an enzyme (β-glucuronidase) in breast milk. Breast milk jaundice is common in breastfed babies and is physiologically normal and nothing to worry about.
Normal bilirubin level for a newborn
It’s normal to have some bilirubin in your blood. Normal bilirubin levels for older children and adults should be at or below 1mg/dL (milligrams per deciliter).
Almost all babies have increased bilirubin levels within 1-2 days of birth. Newborn jaundice (neonatal hyperbilirubinaemia) is diagnosed when blood levels of bilirubin are over 5mg/dL.
The below bilirubin levels are according to the American Academy of Family Physicians:
- Physiological jaundice in healthy term babies usually sees bilirubin levels of about 5-6mg/dL on day 4 after birth, then dropping over the next week until reaching normal levels.
- Breastfed babies are more likely than formula fed babies to develop moderate jaundice with levels up to 12 mg/dL. This is called breast milk jaundice and is considered to be an extended form physiological jaundice.
- Newborns with multiple risk factors may also develop an exaggerated form of physiological jaundice, with bilirubin levels as high as 17mg/dL.
- Around 30% of healthy breastfed babies will develop breast milk jaundice. This usually begins around 5 days after birth and levels are between 12-20mg/dL. Levels usually begin to fall around 2 weeks after birth but around 10% of babies have elevated levels at one month post birth and it may last until 12 weeks.
- Pathological jaundice is marked by the appearance of jaundice within 24 hours after birth, a rising bilirubin level of more than 5mg/dL per day, and a bilirubin level higher than 17 mg/dL in a full term newborn. There are a number of disorders that cause pathological jaundice such as biliary atresia.
What if my baby has high bilirubin levels?
While it’s very common for bilirubin levels to be elevated in newborns for the first few days of life, if levels are 20mg/dL or more, severe jaundice (hyperbilirubinemia) is diagnosed. Less than 2% of babies will develop severe hyperbilirubinemia.
The main factors that your baby’s doctor will consider are:
- How old your baby is (how many hours/days after birth jaundice develops)
- How fast the level is rising
- Whether your baby was born early (premature).
There are two forms of bilirubin can be measured by laboratory tests and can help determine the cause and treatment for hyperbilirubinemia:
- Indirect or unconjugated bilirubin – when red blood cells are broken down, bilirubin is formed and is carried by proteins to the liver. Small amounts may be present in the blood.
- Direct or conjugated bilirubin – is formed in the liver when bilirubin combines with sugars (conjugated), enters the bile and is eventually eliminated by the stool. Under normal conditions conjugated bilirubin is not present in the blood.
In rare cases high levels of unconjugated bilirubin can be toxic and damage developing brain cells, leading to a type of brain damage called kernicterus.
Full term babies who have risk factors and premature babies can develop kernicterus at lower levels of bilirubin than healthy full term babies. Long-term effects of kernicterus are learning and developmental disabilities, hearing loss, movement problems, eye movement problems, and death.
The exact level that is linked to kernicterus in a healthy full term newborn is not known and the occurrence is rare – developing in 1:100,000 babies. There are a number of factors which influence toxicity of the brain, such as ethnicity, underlying disease, and how old the baby is.
When is treatment for jaundice necessary?
If your baby is thought to have jaundice, it may be recommended to test bilirubin levels. There are two ways to test:
- Bilirubinometer: a device which beams light onto your baby’s skin. The meter analyses how the beams of light are reflected off the skin, or absorbed by the skin, then calculates the level of bilirubin in the blood.
- Blood or serum test: a sample of blood that is usually obtained by pricking your baby’s heel with a needle. The level of bilirubin in the liquid part of the blood (the serum) is measured, and the types of bilirubin that are elevated.
Treatment is recommended if bilirubin levels reach:
- 15mg/dL in newborns 25-48 hours old
- 18 mg/dL in newborns 49-72 hours old
- 20 mg/dL in newborns older than 72 hours
Phototherapy is a very effective treatment for hyperbilirubinemia and is used widely. The therapy dosage varies depending on gender, gestational age and time since birth. Depending on where you live and your baby’s risk level phototherapy in your home may be an option. If your baby’s risk level is high, hospital admission for phototherapy is usually necessary.
Newborn jaundice is common and rarely poses a health risk to your baby. However, if jaundice does occur, it’s important to monitor it. Find out more about newborn jaundice.
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