Brain damage in babies most often results from oxygen deprivation during or around birth, but infections, severe jaundice, genetic metabolic conditions, and prenatal exposure to toxins like alcohol can also cause lasting harm. Some of these causes are preventable, others are treatable if caught early, and a few are unavoidable. Understanding what leads to brain injury helps parents recognize warning signs and grasp what happened if their child has been diagnosed.
Oxygen Deprivation During Birth
The single most common cause of serious brain damage in newborns is a lack of oxygen, a condition doctors call hypoxic-ischemic encephalopathy (HIE). This happens when the baby’s brain doesn’t get enough oxygen or blood flow, typically during labor and delivery. A compressed or prolapsed umbilical cord, placental abruption (where the placenta separates from the uterine wall too early), prolonged labor, or a drop in the mother’s blood pressure can all trigger it.
What makes oxygen deprivation so damaging is a two-phase process. First, brain cells run out of energy and swell rapidly, killing tissue outright. Then, after a brief period where things seem to stabilize, a second wave of cell death begins. This delayed phase can continue for hours or even days, which is why early treatment matters so much. The standard intervention is therapeutic hypothermia, where the baby’s body temperature is lowered to slow this second wave of damage. Treatment typically begins within the first several hours of life, with babies reaching the target cooling temperature at a median of about 4.3 hours after birth.
Infections Before and After Birth
Certain infections passed from mother to baby during pregnancy can disrupt brain development while it’s still happening. These are collectively known as TORCH infections: toxoplasmosis, rubella, cytomegalovirus (CMV), and herpes simplex virus. Each of these pathogens can cross the placenta and interfere with how the fetal brain forms, potentially causing an abnormally small head (microcephaly), seizures, and learning disabilities that become apparent after age two. CMV is one of the most common culprits, and many mothers carry it without knowing.
Infections acquired after birth pose a different kind of threat. Bacterial meningitis, an infection of the membranes surrounding the brain, is particularly devastating in newborns. Among babies who survive neonatal meningitis, 25 to 50% develop significant problems with language, movement, hearing, vision, or thinking skills. Between 5 and 20% go on to have epilepsy. In a large study tracking over 1,500 survivors to age five, about 65% of babies who survived Group B strep meningitis had no reported problems, but only 41.5% of those who survived E. coli meningitis escaped without lasting effects. Hearing loss was the most common issue, affecting roughly one in four survivors.
Severe Jaundice and Kernicterus
Nearly all newborns develop some degree of jaundice, the yellowish skin tone caused by a buildup of bilirubin, a byproduct of breaking down red blood cells. In most cases it clears on its own or with light therapy. But when bilirubin levels climb dangerously high and go untreated, the substance crosses into the brain and causes a form of permanent damage called kernicterus.
The risk threshold is generally considered to be a bilirubin level above 25 mg/dL, which occurs in roughly 1 in 2,840 live births. At that level, the risk of brain damage is real but relatively low. When levels exceed 30 mg/dL, the odds shift dramatically: about 1 in 6 to 7 babies at that level will develop kernicterus. It’s worth noting that some babies develop kernicterus even with levels below 25 mg/dL, which is why hospitals screen for jaundice before discharge. Kernicterus can cause cerebral palsy, hearing loss, and problems with eye movement and coordination. It is almost entirely preventable with timely monitoring and treatment.
Birth Trauma and Bleeding
Physical injury during delivery can occasionally cause bleeding inside the skull, known as intracranial hemorrhage. This is more likely during difficult deliveries where instruments are needed. In a large population study of over 125,000 deliveries, babies born with vacuum assistance had roughly 3.7 times the risk of intracranial hemorrhage compared to those born through spontaneous vaginal delivery. The important context: the absolute risk remains very small. Out of nearly 6,600 vacuum-assisted births in the study, three cases of brain bleeding were recorded. So while the relative risk is higher, the actual number of affected babies is low.
Brain bleeds in newborns range from minor, where a small amount of blood is reabsorbed without lasting effects, to severe, where large bleeds cause pressure on the brain and permanent injury. Premature babies are especially vulnerable because their blood vessels are more fragile.
Metabolic and Genetic Conditions
Some babies are born with inherited metabolic disorders that cause toxic substances to build up in the brain. These conditions are rare individually, but collectively they represent an important cause of newborn brain injury.
The most time-sensitive of these involve ammonia buildup. Ammonia is directly toxic to brain cells, and the extent of damage depends on how high levels climb and how long they stay elevated. Urea cycle defects, where the body can’t properly process nitrogen from protein breakdown, are the primary culprit. Organic acidurias like methylmalonic acidemia and propionic acidemia also cause dangerous ammonia spikes along with other toxic byproducts.
Maple syrup urine disease (named for the sweet smell it gives to urine) is another example. Babies with this condition can’t break down certain amino acids, and one of them, leucine, is particularly harmful to the brain. Symptoms typically appear in the first week of life as the baby becomes increasingly unresponsive. Non-ketotic hyperglycinemia, another metabolic disorder, can cause severe, hard-to-treat seizures within the first hours or days after birth. Most of these conditions are now included in newborn screening panels, which means a heel-prick blood test taken shortly after birth can catch them before serious damage occurs.
Prenatal Alcohol and Toxin Exposure
Alcohol is one of the most well-documented substances that can damage a developing baby’s brain. Prenatal alcohol exposure can cause fetal alcohol spectrum disorders, with fetal alcohol syndrome (FAS) being the most severe form. Imaging studies of children with FAS show measurable changes in brain structure, including reduced size or altered shape of the corpus callosum (the band of fibers connecting the two brain hemispheres), the cerebellum (which coordinates movement and balance), and the basal ganglia (involved in motor control and learning). Head circumference in affected children often falls below the 10th percentile for age and sex, reflecting overall smaller brain size.
The effects aren’t limited to brain structure. Children with fetal alcohol spectrum disorders commonly struggle with attention, memory, impulse control, and social skills. Unlike some other causes of brain damage, there’s no threshold amount of alcohol that’s been proven safe during pregnancy, and the damage occurs during development, meaning it can’t be reversed after birth.
Premature Birth
Babies born very early, particularly before 32 weeks of gestation, face elevated risk of brain injury simply because their brains are still in a critical stage of development. The blood vessels feeding the brain are fragile and prone to rupture, leading to intraventricular hemorrhage (bleeding into the fluid-filled spaces of the brain). The surrounding brain tissue, still forming its insulation and connections, is also vulnerable to injury from inflammation, infection, or drops in oxygen.
The earlier a baby is born, the higher the risk. Many premature infants go on to develop normally, but those who experience significant brain bleeds or white matter injury face increased chances of cerebral palsy, cognitive delays, and learning difficulties later in childhood.