If you have noticed your newborn's skin or the whites of their eyes taking on a yellowish tinge in the first few days of life, you are almost certainly looking at neonatal jaundice — and you are far from alone. Jaundice is one of the most common conditions seen in newborns, affecting around six in ten full-term babies and an even higher proportion of those born prematurely. For the vast majority of families, it is a normal, self-resolving part of the newborn period that requires nothing more than a few extra feeds and careful watching.
That said, jaundice exists on a spectrum. While mild jaundice is harmless, severe jaundice that is not caught and treated in time can in rare cases affect the brain. Knowing how to tell the two apart — and when to call your doctor — is exactly what this article is designed to help you do.
Tracking your newborn's colour, feeding patterns, and wet nappy count in the early weeks can make it much easier to spot a change. The Healthbooq app at healthbooq.com is designed for precisely this kind of daily observation, giving you a clear record to share with your midwife or paediatrician at check-ups.
What Causes Jaundice in Newborns?
Jaundice is caused by a build-up of bilirubin, a yellow pigment that is produced when red blood cells break down. Before birth, the placenta handles the removal of bilirubin from the baby's bloodstream. After birth, that job falls to the liver — which, in a newborn, is still immature and not yet fully efficient at processing bilirubin quickly. At the same time, newborns have more red blood cells than they will need in later life, and the body begins breaking down the excess foetal haemoglobin in the first days after birth. The combination of high bilirubin production and a liver that is still finding its feet is why jaundice appears so commonly and so predictably.
This type of jaundice — called physiological jaundice — typically appears on the second or third day of life, peaks around day four or five in full-term babies, and fades on its own by two weeks. It is not a sign that anything is wrong, and it does not require treatment unless bilirubin levels rise to a point where they need to be actively managed.
Types That Need Closer Attention
Beyond physiological jaundice, there are a few other forms that doctors watch for more carefully. Jaundice that appears within the first 24 hours of life is always considered significant and should be assessed promptly, because this early onset can indicate a blood type incompatibility between mother and baby or a condition affecting the red blood cells. Equally, jaundice that persists beyond two weeks in a full-term baby — or beyond three weeks in a premature baby — warrants investigation to rule out causes such as a blocked bile duct or an underactive thyroid, even though both of these are rare.
Breastfeeding jaundice is another pattern worth knowing about. In the first week, it is sometimes associated with insufficient milk intake — a baby who is not feeding well and not producing enough wet nappies may be slightly dehydrated, which can slow the liver's clearance of bilirubin. This is one of the reasons midwives pay close attention to feeding frequency and urine output in the early days. The solution is nearly always to feed more frequently, and in some cases to have feeding technique assessed by a lactation consultant, rather than to switch to formula.
How Jaundice Is Assessed
When your midwife or paediatrician suspects jaundice, they will usually start with a transcutaneous bilirubinometer — a small device that shines light through the skin and estimates bilirubin levels without a blood test. If that reading is elevated, a blood test from a heel-prick will confirm the exact level. The result is then plotted on a chart that takes your baby's age in hours and gestational age into account, because what counts as "high" changes significantly in the first days of life.
Treatment is typically phototherapy, where the baby lies under special blue-spectrum lights that break down bilirubin in the skin. It is safe, effective, and usually only required for one to three days. For very high levels, exchange transfusion is occasionally needed, but this is rare.
What to Watch For at Home
In the first two weeks, check your baby's skin each day in natural light or under a white ceiling light — artificial lighting can make it harder to detect yellowing, especially in babies with darker skin tones. Press gently on the skin and see if it looks yellow underneath as the blood clears. Start at the face — jaundice tends to progress from the head downward — and note if the yellowing is moving toward the abdomen and legs, which is a sign that levels are rising.
Alongside colour, watch your baby's feeding closely. A baby with high bilirubin levels often becomes very sleepy and difficult to rouse for feeds, which then makes the jaundice worse because feeding is the main mechanism by which bilirubin is excreted. If your baby is sleeping through feeds and is difficult to wake, contact your midwife or maternity unit that day.
Call your healthcare provider promptly if the jaundice appeared in the first 24 hours, if the yellowing has spread to the arms and legs, if your baby is unusually difficult to wake, if they are feeding poorly or producing fewer than six wet nappies in 24 hours, or if they appear unwell in any way.
Key Takeaways
Mild jaundice is extremely common in newborns — around 60% of full-term babies develop it in the first week. It is caused by a normal build-up of bilirubin as the body clears foetal red blood cells. Most cases resolve on their own within two to three weeks and do not require treatment. Severe or persistent jaundice does need medical attention, and knowing the warning signs is important. Premature babies and those with certain blood type differences are at higher risk and should be monitored more closely.
