Most newborn jaundice is treated with phototherapy, a safe and effective light-based treatment that breaks down excess bilirubin in your baby’s skin so it can be excreted without needing to pass through the liver. About 60% of full-term and 80% of preterm babies develop some degree of jaundice in their first week of life, and the vast majority resolve with a combination of frequent feeding and, when needed, phototherapy. Understanding how these treatments work can help you feel more confident navigating those early days.
Why Newborns Get Jaundice
Jaundice happens when bilirubin, a yellow pigment produced by the normal breakdown of red blood cells, builds up faster than your baby’s body can get rid of it. Newborns produce roughly twice as much bilirubin as adults because their red blood cells have a shorter lifespan (about 52 days compared to 120 days in adults). On top of that, a newborn’s liver can conjugate, or process, bilirubin at only about 1% of an adult liver’s capacity. That processing ability ramps up quickly over the first 90 days of life, but in those initial days, there’s a real bottleneck.
There’s also a recycling problem. Bilirubin that does make it into the intestines can get converted back into its original form and reabsorbed into the bloodstream. This loop, called enterohepatic circulation, is stronger in newborns because their gut microbiome is still developing. Breast milk contains an enzyme that contributes to this reconversion, which is one reason breastfed babies are slightly more prone to jaundice. The combination of high production, low processing, and intestinal reabsorption is why bilirubin levels climb so predictably in the first few days.
How Jaundice Is Detected
Your baby’s care team will visually check for the yellow tint of jaundice in the skin and eyes, but visual assessment alone isn’t reliable enough to guide treatment decisions. Many hospitals now use a transcutaneous bilirubinometer, a handheld device pressed against the baby’s forehead or chest that estimates bilirubin levels through the skin. It’s painless and takes seconds. Studies show these devices are highly sensitive for ruling out dangerous bilirubin levels, meaning if the reading is low, you can trust it.
If the transcutaneous reading is elevated, a blood draw is needed to measure the total serum bilirubin (TSB) precisely. This blood test is the gold standard, and treatment decisions, including whether to start phototherapy, are based on TSB results plotted against your baby’s age in hours, gestational age, and any risk factors for bilirubin-related brain injury.
Frequent Feeding as a First-Line Strategy
Feeding your baby 8 to 12 times per day is one of the most effective things you can do to help clear bilirubin. Each feeding stimulates the gut, moving bilirubin-laden stool through the intestines before it can be reabsorbed. Frequent feeding also keeps your baby well hydrated and calorie-fueled, which supports the liver’s ability to process bilirubin. For breastfeeding mothers, the frequent sessions have the added benefit of building milk supply during those critical early days.
There’s an important distinction between two types of jaundice linked to breastfeeding. “Breastfeeding jaundice” appears in the first week and is caused by insufficient milk intake, usually because feeding hasn’t been fully established yet. Increasing feeding frequency and working with a lactation consultant typically resolves it. “Breast milk jaundice” appears later, often in the second or third week, and is related to substances in breast milk that increase bilirubin reabsorption. It’s generally harmless and resolves on its own over several weeks. In neither case does stopping breastfeeding need to be the answer.
Phototherapy: How It Works
Phototherapy is the primary medical treatment for newborn jaundice. It uses blue light at a wavelength of 450 to 470 nanometers, the range most efficiently absorbed by bilirubin. When this light penetrates your baby’s skin, it triggers a chemical reaction called photoisomerization: bilirubin molecules change shape into water-soluble forms that can bypass the liver entirely and be excreted through bile and urine.
A second reaction, called structural isomerization, also occurs. This converts a small amount of bilirubin into a compound called lumirubin, which is permanently altered and excreted in both bile and urine without any chance of being reabsorbed. While this pathway accounts for a smaller share of bilirubin clearance, it’s especially useful because the conversion is irreversible.
During phototherapy, your baby will lie under the lights wearing only a diaper and protective eye shields. The goal is to expose as much skin as possible. In some setups, a fiberoptic blanket is placed underneath the baby to provide light from below at the same time. Sessions are continuous, with breaks for feeding and diaper changes, and bilirubin levels are rechecked every 4 to 12 hours depending on severity. Most babies need phototherapy for 1 to 2 days before their levels drop enough to safely stop.
What Triggers the Decision to Start Treatment
The 2022 guidelines from the American Academy of Pediatrics use hour-specific bilirubin thresholds to determine when phototherapy should begin. These thresholds aren’t a single number. They vary based on three factors: how many hours old your baby is, their gestational age, and whether any neurotoxicity risk factors are present.
Risk factors that lower the treatment threshold include:
- Gestational age below 38 weeks, with risk increasing the more premature the baby is
- Low albumin levels (below 3.0 g/dL), since albumin is the protein that carries bilirubin safely through the blood
- Hemolytic conditions, where red blood cells break down faster than normal due to blood type incompatibility (Rh or ABO), G6PD deficiency, or other causes
- Sepsis or significant clinical instability in the previous 24 hours
A baby with one or more of these risk factors will have a lower bilirubin threshold for starting phototherapy compared to a healthy full-term baby with none. This is why two babies of the same age can have identical bilirubin levels but receive different recommendations.
Home Phototherapy
Some babies qualify for phototherapy at home using a fiberoptic blanket or pad, which wraps around the baby and delivers light directly to the skin. Home phototherapy is typically offered when bilirubin levels are only moderately elevated and the baby is otherwise healthy, feeding well, and at least 37 weeks gestational age. The practical considerations matter too: how far you live from the hospital, whether follow-up blood draws can be arranged, and how comfortable you feel managing the equipment.
There isn’t strong comparative evidence showing whether home phototherapy works as well as hospital-based treatment with overhead lamps, which are generally more powerful. A Cochrane review found no high-quality studies meeting its criteria for this comparison. In practice, hospitals reserve the most intensive overhead phototherapy for babies with higher bilirubin levels, while home blankets serve as a step-down option for milder cases.
When Phototherapy Isn’t Enough
In rare cases where bilirubin continues to rise despite intensive phototherapy, or when a baby shows signs of acute bilirubin encephalopathy (brain injury from bilirubin), more aggressive treatments are used.
Intravenous Immunoglobulin
When jaundice is caused by a blood type mismatch between mother and baby, such as Rh or ABO incompatibility, the mother’s antibodies attack the baby’s red blood cells, releasing a surge of bilirubin. Intravenous immunoglobulin (IVIG) can slow this destruction. It’s typically considered when bilirubin levels are climbing toward the exchange transfusion threshold despite phototherapy, and it can sometimes prevent the need for that more invasive procedure.
Exchange Transfusion
Exchange transfusion is the last resort. It involves gradually removing small volumes of the baby’s blood and replacing them with donor blood, physically washing out the excess bilirubin. This procedure is reserved for the most severe situations: when bilirubin reaches levels associated with brain damage (research identifies levels at or above 27.5 mg/dL as particularly dangerous for classic kernicterus), when bilirubin keeps rising despite maximum phototherapy, or when a baby shows neurological warning signs like extreme sleepiness, a high-pitched cry, arching of the back, poor feeding, or seizures.
Exchange transfusion carries real risks, including blood pressure instability, low calcium, infection, and cardiac complications. It’s performed in a neonatal intensive care unit with continuous monitoring. Fortunately, with early screening and accessible phototherapy, the need for exchange transfusion has become very uncommon.
Why Bilirubin Levels Matter
The reason jaundice is taken seriously isn’t the yellow skin itself. It’s what very high bilirubin can do to the brain. Bilirubin at moderate levels is harmless and may even act as an antioxidant. But when levels climb well above treatment thresholds and remain elevated, bilirubin can cross into the brain and damage specific areas responsible for hearing, movement, and coordination.
Acute bilirubin encephalopathy is the early, potentially reversible phase. A baby may become unusually lethargic, feed poorly, develop a high-pitched cry, or show abnormal muscle tone. If bilirubin levels are brought down quickly at this stage, many babies recover fully. Kernicterus is the permanent form of damage, and it can cause lifelong problems with movement, hearing loss, and developmental delays. The key to prevention is catching rising bilirubin early, which is why most hospitals check levels before discharge and schedule follow-up within 1 to 2 days.