Newborn Jaundice: What It Is, What Causes It, and What to Do

You are in the hospital, probably running on zero sleep, trying to absorb an enormous amount of information in a very short time. And then someone says: "The baby looks a little yellow. We are going to monitor for jaundice."

Your stomach drops. Yellow? That does not sound good. The word "jaundice" has a vaguely serious ring to it. You start catastrophising quietly while trying to look calm for your partner.

Here is what you need to know: newborn jaundice is extremely common, usually harmless, and almost always resolves on its own within two weeks. It is not a sign that something is badly wrong. But it does need to be understood and, in some cases, monitored carefully.

This guide covers everything: what jaundice is, why it happens, what the numbers mean, when treatment is needed, and when to actually worry.

What Is Newborn Jaundice?

Jaundice is a yellow tinge to the skin and the whites of the eyes, caused by a build-up of a substance called bilirubin in the blood. Bilirubin is produced when red blood cells break down, which is a completely normal process. The liver's job is to process it and move it out of the body through stools.

In newborns, the liver is not yet fully up to speed. It can be slow to process bilirubin efficiently, so levels build up temporarily in the blood. The yellow colour you can see in the skin is simply bilirubin accumulating in the tissue.

This is called physiological jaundice, and it is a normal part of newborn development, not an illness.

How Common Is It?

Very. According to the NHS, jaundice affects around 60% of full-term babies and up to 80% of premature babies in their first week of life. In other words, more than half of all newborns will show some degree of yellowing. Your midwife and health visitor check for it routinely because it is so common, not because it is alarming.

Most cases are mild, need no treatment beyond feeding well, and clear up completely by the time the baby is two weeks old.

What Does Jaundice Actually Look Like?

The yellow tinge usually appears first on the face, particularly around the forehead and nose, then spreads downwards to the chest, abdomen, arms, and legs as bilirubin levels rise. The whites of the eyes (the sclera) often show it clearly too.

Mild jaundice can be subtle and easy to miss, especially under hospital lighting. One reliable way to check: press gently on the skin with a fingertip, release, and look at the skin colour where you pressed. A yellowish tinge underneath is a sign of jaundice.

Checking for Jaundice in Babies with Darker Skin

If your baby has brown or Black skin, the yellow tinge can be much harder to spot. Focus on areas with less pigmentation: the whites of the eyes, the gums, the palms of the hands, and the soles of the feet. These areas tend to show yellowing more clearly. If you have any doubt, ask your midwife for a bilirubin check, which can be done quickly with a skin probe.

Why Does Jaundice Happen?

Newborns arrive with a high concentration of red blood cells, more than they will need once they are breathing air rather than relying on the placenta. In the first days of life, those extra red blood cells break down rapidly. Each one releases bilirubin. The liver has to process all of it, but the newborn liver takes a few days to get running at full capacity. The result is a temporary backlog: bilirubin builds up faster than it can be cleared.

There are a few specific scenarios worth knowing about:

Breastfeeding Jaundice

In the first few days after birth, if your partner's milk has not fully come in yet, the baby may not be getting quite enough fluid. Low fluid intake means fewer bowel movements, which means bilirubin is not being expelled from the body as quickly as it should be. This is why feeding frequency matters so much in those early days. It is not that breastfeeding causes jaundice, it is that insufficient feeding slows the clearance of it.

Later, a small number of breastfed babies develop what is called breastmilk jaundice, where a substance naturally present in breastmilk appears to slow bilirubin processing slightly. This is harmless, tends to resolve slowly over several weeks, and is not a reason to stop breastfeeding. Your midwife or GP will advise if they think this applies.

Blood Group Incompatibility

If your baby's blood type is incompatible with your partner's, the mother's antibodies can cross the placenta and begin breaking down the baby's red blood cells before birth and in the early days after. This can cause bilirubin to rise faster than usual. It is more likely with certain blood type combinations and is something the maternity team will be aware of if there is a risk.

Bruising from Birth

A difficult delivery, forceps use, or a significant bruise from birth trauma can cause blood cells to break down in the bruised tissue, releasing extra bilirubin. Babies born with cephalhaematomas (a bruise on the skull from delivery) are at higher risk of jaundice for this reason.

What Happens at the Hospital: Tests and Monitoring

Your midwife will visually check your baby for jaundice at every postnatal visit. If they suspect levels are elevated, they will do a bilirubin check using either:

• A transcutaneous bilirubinometer (TcB): A small device pressed against the skin that gives a reading in seconds. Non-invasive and painless.
• A heel prick blood test (serum bilirubin, or SBR): A tiny blood sample taken from the baby's heel. More accurate and used to confirm readings or in cases where treatment is being considered.

The result is plotted on a chart against the baby's age in hours. This is important: a bilirubin level that is fine at 30 hours old might need treatment at 48 hours old. The thresholds change with age, which is why the hospital plots the number on a curve rather than giving you a single cut-off figure.

If levels are below the treatment threshold and the baby is otherwise well, they will monitor and recheck. If levels are approaching or crossing the treatment line, phototherapy will be recommended.

Treatment: What Actually Happens

More Frequent Feeding

The first and most important intervention for mild jaundice is simply feeding more often. Breast or bottle, more frequent feeds mean more bowel movements, and more bowel movements mean bilirubin is being expelled from the body faster. The NHS recommends 8 to 12 feeds in 24 hours in the early days. This is not just good for milk supply, it actively helps clear jaundice.

If breastfeeding is proving difficult and levels are rising, the team may suggest supplementing with formula temporarily to ensure the baby is getting enough fluid. This is a pragmatic, short-term decision, not a failure. Read more about how to support your partner through breastfeeding challenges.

Phototherapy (Light Therapy)

If bilirubin levels cross the treatment threshold for your baby's age, phototherapy will be started. The baby is placed under a special blue-spectrum light (or wrapped in a light blanket called a Biliblanket) with their eyes covered for protection. The light works by converting bilirubin in the skin into a form that can be excreted in urine without needing to be processed by the liver.

It looks alarming if you are not prepared for it. Your tiny baby, naked except for a nappy and tiny eye patches, under a glowing blue light. It is a lot. But phototherapy is safe, effective, and typically works within 24 to 48 hours. Levels are checked regularly, and the light is turned off once they come back down into the safe zone.

During phototherapy, the baby will be taken out for feeds and brief cuddles. Skin-to-skin time is paused temporarily, which is hard, but it is temporary. Stay present. You are not failing by letting the machine do its job.

Exchange Transfusion (Rare)

In a very small number of severe cases, if phototherapy does not bring levels down quickly enough, an exchange transfusion may be needed. The baby's blood is gradually replaced with donor blood, rapidly reducing bilirubin concentration. This is uncommon and typically only used when levels are dangerously high or rising very fast. If this is mentioned, ask for a clear explanation of the numbers and the timeline. It is a significant intervention but a well-established one.

How to Help at Home

If your baby has mild jaundice and is being discharged, here is what you can do:

• Feed frequently. Wake the baby if necessary. 8 to 12 times in 24 hours in the first week. Jaundice makes babies sleepy, which makes them feed less, which makes jaundice worse. Break the cycle by rousing them to feed.
• Watch for warning signs. Yellowing spreading to the legs and feet, or the baby becoming increasingly sleepy and difficult to rouse, are signs to call your midwife or go to A&E.
• Keep follow-up appointments. Your midwife or health visitor will recheck bilirubin levels in the days after discharge. Do not skip these.
• Skip the sunlight advice. You may read that putting the baby near a window in sunlight helps. There is some theoretical basis to this (sunlight contains the blue spectrum), but it is uncontrolled, risks sunburn on newborn skin, and should not replace monitoring by a professional. Stick to the proper checks.

For general guidance on when to call the doctor or go to hospital with a baby, including fever, breathing concerns, and feeding problems, that article walks through the key thresholds clearly.

Frequently Asked Questions About Newborn Jaundice

Is newborn jaundice dangerous?

In the vast majority of cases, no. Most newborn jaundice is mild, resolves on its own within two weeks, and causes no harm. Severe jaundice, if left untreated, can cause a rare condition called kernicterus (bilirubin-induced brain damage), but this is very uncommon in countries with routine newborn screening. The checks your midwife and health visitor do in the first few days exist precisely to catch levels before they reach that point.

How long does newborn jaundice last?

Most cases clear up within 10 to 14 days, according to NHS guidance. In breastfed babies, it can occasionally persist for up to three weeks or slightly longer. If your baby still looks yellow after three weeks, take them to your GP for a check. It will almost certainly be fine, but it is worth investigating to rule out less common causes.

Can I do anything to prevent jaundice?

Not entirely. Physiological jaundice is a normal part of newborn development and cannot be fully prevented. What you can do is feed frequently from birth, 8 to 12 times in 24 hours, which helps the baby pass bilirubin through stools. Early, effective feeding is the single biggest thing that reduces the risk of jaundice becoming severe.

Is jaundice worse in breastfed babies?

Breastfed babies do have a slightly higher rate of jaundice, for two reasons. In the first few days, if milk supply is not yet established and the baby is not feeding well, they can become mildly dehydrated, which concentrates bilirubin. Later, a small percentage of breastfed babies get what is called breastmilk jaundice, where a substance in the milk slows bilirubin processing. This is not harmful and is not a reason to stop breastfeeding. Your midwife will advise on feeding frequency if levels are borderline.

My baby still has yellow skin at three weeks. Should I be worried?

If your baby is feeding well, gaining weight, and the yellowing is mild, it is likely breastmilk jaundice, which is harmless. However, any jaundice persisting beyond three weeks should be checked by a GP. They will look for other causes such as a bile duct problem or thyroid issue. These are uncommon, but three weeks is the threshold where you stop watching and start investigating.

How do I check for jaundice in a baby with darker skin?

Yellow tones can be harder to spot on brown or Black skin. Focus on areas where pigmentation is naturally lighter: the whites of the eyes, the gums, the palms of the hands, and the soles of the feet. Pressing gently on the skin and releasing can also reveal a yellowish tinge underneath. When in doubt, ask your midwife to do a bilirubin check with a skin probe.

The Bottom Line

Newborn jaundice is one of those things that sounds frightening and turns out to be mostly fine. More than half of all babies get it. Most do not need any treatment beyond feeding well and being monitored. The ones that do need phototherapy almost always respond quickly, and the whole thing is forgotten within a week.

Your job is to understand what to watch for, feed the baby frequently, keep the follow-up appointments, and not spiral into catastrophising at 3am. The system of checks exists for exactly this reason, and it works.

If you are still finding your feet with the practical side of newborn care, bonding with your newborn as a dad is worth reading, along with what a realistic newborn sleep schedule looks like in the first six weeks. Neither of those things require a yellow baby to be relevant.