Newborn Jaundice and Breastfeeding: Why Babies Turn Yellow and How Feeding Helps

Newborn jaundice is a yellowing of the skin and eyes caused by a build up of bilirubin, and it affects about 6 in 10 full-term babies and 8 in 10 premature babies in the first week, usually most noticeable around day 3 and fading by about 2 weeks.¹² It overlaps almost exactly with the days when breastfeeding is getting established, which is why the two are so often mentioned together, and why the most common advice for a mildly yellow baby is simply to feed more.

With my first, the yellow arrived on about day four, the same week as the shallow latch and the engorgement. The midwife held a little meter to the baby’s forehead, read the number, and said two things I have never forgotten: the level was below the line where treatment starts, and we needed to wake the baby for feeds rather than wait to be asked. I spent the next few days staring at skin colour under every lamp in the house. It faded by about two weeks, but I would have slept better knowing what was normal, what helped, and what was a reason to call. Here is that picture, checked by a paediatrician.

What newborn jaundice is and why it happens

Jaundice happens because newborns break down a lot of red blood cells after birth and their liver is not yet efficient at clearing the bilirubin this produces. Bilirubin is a yellow pigment. Before birth the placenta handled it; afterwards the baby’s own liver has to process it so it can leave the body in the stools. In the first few days that system is still warming up, so bilirubin builds up in the blood and shows in the skin².

Most of this is physiological jaundice: a normal, temporary stage that peaks around day 3 to 5 and fades without treatment. A smaller number of babies have jaundice caused by something else, such as a blood group difference with the mother, an infection, or, rarely, a liver problem. The timing and the baby’s overall condition are what help clinicians tell these apart, which is why guidance treats jaundice in the first 24 hours of life as a reason for an urgent check rather than watching and waiting¹.

Some babies are more likely to become noticeably jaundiced. NICE lists being born before 38 weeks, having a brother or sister who needed phototherapy, and a plan to breastfeed exclusively as risk factors for significant jaundice¹. That last one is not a reason to avoid breastfeeding; it is a reason for midwives to keep a closer eye on feeding in the first week.

How breastfeeding and jaundice are linked

Breastfeeding does not cause dangerous jaundice, but a baby who is not yet feeding well clears bilirubin more slowly, so slow early feeding can make jaundice deeper. Bilirubin leaves the body mainly in the stools. Colostrum has a gentle laxative effect that helps a newborn pass meconium, the dark sticky first stool, and with it a large load of bilirubin. A baby who feeds often moves through meconium faster; a sleepy baby taking very little does not.

This is where the two ideas get tangled, so it helps to separate them. Clinicians often talk about two patterns:

• Early jaundice linked to low intake (sometimes called breastfeeding jaundice or suboptimal intake jaundice). It shows in the first week when feeds are infrequent or ineffective, often alongside a shallow latch, more than the expected weight loss, and fewer wet and dirty nappies. The answer is more frequent, more effective milk removal.
• Breast milk jaundice. This appears in a baby who is feeding and growing well, and lasts beyond the first two weeks, sometimes for 2 to 3 months. It is thought to involve substances in breast milk that slow bilirubin processing for a while. It is harmless once other causes have been ruled out.

The first pattern is the one that overlaps with feeding problems. A newborn’s stomach holds only about 5 to 7 ml on day 1, and milk usually comes in between day 2 and 5, so the first days are always small volumes. That is normal. What matters is that the small feeds are frequent; the guide to colostrum and the first days explains why those early feeds do so much.

How to help a jaundiced baby feed well

Frequent, effective breastfeeding, about 8 to 12 times or more in 24 hours, is the first and most important thing you can do for a mildly jaundiced baby.³ Jaundice tends to make babies sleepier, and sleepy babies ask for fewer feeds, which can slow bilirubin clearance further. Breaking that loop is the whole point.

Practical things that helped me, and that midwives commonly suggest:

• Wake for feeds. If your baby is jaundiced and sleepy, do not let gaps stretch past about 3 hours in the early days unless your midwife says otherwise. Undressing to the nappy, a nappy change, or skin to skin often rouses a drowsy baby.
• Use breast compression. Gently squeezing the breast when sucking slows keeps milk flowing to a baby who drifts off mid feed.
• Switch sides when swallowing tails off, rather than letting a sleepy baby comfort suck with little milk moving.
• Get the latch checked. A shallow latch moves less milk; a deep one moves more. A midwife or lactation consultant watching one full feed can make a big difference.
• Express if needed. If your baby is too sleepy to feed effectively, hand expressing colostrum and giving it by syringe or cup keeps milk going in and protects your supply.

Do not give water or sugar water. NICE advises against giving additional fluids to breastfed babies having phototherapy, and prefers your expressed milk if an extra feed is needed¹. Water does not lower bilirubin and fills a tiny stomach that should be taking milk. The American Academy of Pediatrics likewise recommends supporting and continuing breastfeeding⁴. If a top up of expressed milk or formula is advised for weight or intake, it is usually alongside the breast, not instead of it.

How often to feed in the first weeks, and how to read early hunger cues in a baby who is not giving many, is covered in more depth in how often to breastfeed a newborn.

Signs your baby is getting enough while jaundiced

Nappies and weight are the clearest signs that a jaundiced baby is getting enough milk: by day 5, look for about 6 or more heavy wet nappies and at least 3 to 4 soft yellow stools in 24 hours. Stools changing from black meconium to green and then mustard yellow by around day 4 or 5 is a good sign that milk is coming through and bilirubin is leaving.

Weight helps too. A loss of up to about 7 to 10% of birth weight in the first days is normal, and most babies are back to birth weight by about 10 to 14 days. A baby who has lost more than that, is still passing dark stools after day 5, or has few wet nappies needs a feeding review alongside the jaundice check, because the two problems feed each other. The full set of signs is in is my baby getting enough milk.

Colour in the nappy matters in another way. Pale, chalky, or white stools, or dark yellow urine that stains the nappy, are not part of normal jaundice. NICE flags them as signs that need prompt investigation because they can point to a liver problem¹.

When jaundice needs treatment

Most jaundice needs no treatment, but if the bilirubin level crosses a threshold for your baby’s age in hours, the usual treatment is phototherapy, and breastfeeding normally continues alongside it. Bilirubin is measured with a skin meter (a transcutaneous bilirubinometer) or a small heel prick blood test, and the result is plotted against a chart based on how many hours old the baby is and how many weeks they were born at¹.

Phototherapy uses a special blue light that changes bilirubin into a form the body can pass more easily. The baby lies under the lights or on a light blanket wearing only a nappy, with eye shields. For standard phototherapy, NICE advises short breaks of up to about 30 minutes for feeds, nappy changes, and cuddles¹. If the level is high enough to need continuous treatment, the team may ask you to express so your baby can have your milk without leaving the lights; ask for a pump early so your supply is protected.

Premature babies are more likely to be jaundiced and are treated at lower levels; the guide to breastfeeding a premature baby covers expressing on the neonatal unit. Very high levels that do not respond to phototherapy are rare, and in that situation a specialist team may use an exchange transfusion. Sunlight is not a treatment: NICE advises against using it for neonatal jaundice¹.

Jaundice that lasts beyond two weeks

Jaundice still visible after 14 days in a full-term baby, or 21 days in a premature baby, is called prolonged jaundice and should always be checked, even though in breastfed babies it is usually harmless breast milk jaundice.¹ The check is quick: a look at the baby, questions about stools and urine, and a blood test that separates the two forms of bilirubin to rule out rarer causes such as an underactive thyroid or a liver condition.

If the tests are normal and your baby is feeding well, gaining weight, and producing yellow stools, the yellow tinge can be left to fade, which can take up to about 2 to 3 months. Stopping breastfeeding to “test” the diagnosis is rarely recommended now. The Academy of Breastfeeding Medicine’s guidance is to keep breastfeeding a thriving baby with breast milk jaundice⁵, and the WHO recommends exclusive breastfeeding for about the first 6 months³.

When to call your midwife or doctor

Call 999 or go to A&E if your baby has jaundice and is less than 24 hours old, is sleepier than normal or hard to wake, is not feeding, or is floppy or stiff.² The NHS lists other emergency signs in a jaundiced baby too: no wet nappies, a temperature of 38C or more or 36C or less, or difficulty breathing, such as grunting or the tummy sucking in under the ribs.

Ask for an urgent midwife or GP appointment, or call NHS 111, if your baby is over 24 hours old and:²

• You think they have jaundice.
• They have been diagnosed with jaundice and it is not getting better, or is getting worse.
• Their pee is dark yellow or brown, or their poo is pale and creamy (keep a nappy to show the midwife).

Also get a check if feeds are poor or wet nappies are fewer than about 6 by day 5, or if any yellow colour is still present after 2 weeks (3 weeks if premature)¹.

Looking back, the thing I needed to hear on day four was that a yellow baby who is feeding often, filling nappies, and waking for feeds is almost always on the right path, and that the cure for ordinary jaundice is mostly the same work that builds a supply. This article is general information, not personal medical advice. If your baby looks yellow, ask your midwife to check the level rather than judging it by eye: it takes a minute, and it is the only way to know.