Hypoxic-Ischemic Encephalopathy(HIE)​

Hypoxic-ischemic encephalopathy, or HIE, is the brain injury caused by oxygen deprivation to the brain. When it occurs during birth, it is sometimes referred to as intrapartum asphyxia. HIE is triggered by a combination of an interruption of oxygen circulation, called hypoxia, and ischemia, which refers to blood flow restriction.

Although an infant’s body can compensate for brief periods of oxygen loss, prolonged periods destroy brain tissue. HIE occurs in one to two infants per thousand and can manifest as difficulty breathing, depression of muscle tone and reflexes, a reduced or absent response to stimulation, and seizure.

What is hypoxic-ischemic encephalopathy?

HIE is a severe birth complication that affects preterm and full-term infants, and 40% to 60% of affected infants either die by age two or have severe disabilities. Of those who suffer perinatal HIE, 25% of surviving infants will develop severe and permanent neuropsychological consequences, “including mental retardation, visual motor or perceptive visual dysfunction, increased hyperactivity, cerebral palsy, and epilepsy.”

Causes of Hypoxic-Ischemic Encephalopathy (HIE)

HIE occurs when the brain is deprived of oxygen. A variety of causes can lead to HIE. These causes can occur during fetal development, labor, and delivery, or during the postnatal period.

During Fetal Development

Several factors can cause HIE during fetal development. High-risk pregnancy factors such as preeclampsia, maternal diabetes, and vascular disease can lead to HIE. Preeclampsia occurs when blood pressure increases and the level of protein in the urine rises. It typically occurs in the 20th week of pregnancy and can continue until the baby is born. It can be diagnosed and treated.

A recent study found that mothers who had Type 1 or Type 2 diabetes were at greater risk of delivering babies with HIE. If the mother was obese, the risk was even greater.

Uterine rupture may lead to HIE. Uterine rupture can occur spontaneously or due to another incident, such as trauma. The uterus can rupture during a vaginal delivery after a previous Cesarean delivery has caused scarring and thinning of the uterus.

Problems with the placenta can lead to HIE. For example, placental abruption, which refers to the detachment of the placenta from the inner wall of the uterus, and instances where the placenta covers the opening of the cervix may lead to HIE.

In addition, fetal infections, fetal anemia, and fetal lung malformation, as well as a mother’s drug or alcohol use during pregnancy can cause HIE.

During Labor and Delivery

Several factors during labor and delivery can lead to HIE. The first involves complications with the umbilical cord, such as prolapse and compression. According to the American Pregnancy Association, “[u]mbilical cord compression occurs in approximately 1 in 10 deliveries.”

During labor, constant monitoring of the baby’s heartbeat is critical. Medical professionals can detect oxygen deprivation quickly by looking at the baby’s heart rate. However, if the medical team fails to monitor heartbeat, HIE can occur.

Although HIE can affect full-term babies, preterm babies are at even greater risk of experiencing hypoxic-ischemic encephalopathy. Babies born prematurely are more likely to have underdeveloped lungs and immune systems.

A breech presentation or a delayed delivery can lead to HIE. This can occur in instances of shoulder dystocia, where a baby gets stuck in the birth canal, or in cases where a baby is too large for a vaginal delivery and doctors fail to perform a timely C-section.

During the Postnatal Period

Infants can develop HIE because of postpartum complications. Premature babies are especially at risk of suffering brain injury or death if HIE occurs after delivery. Lung or heart disease or severe infection may cause HIE. Brain or skull trauma or a “near miss” sudden-infant-death-syndrome (SIDS) event can inhibit oxygen and blood flow and cause HIE. A baby’s very low blood pressure or respiratory failure also can be a factor. Babies can develop HIE because of hypoglycemia or hyperglycemia, leading to a hard sugar crash. That crash can cause seizures and a lack of oxygen. Children who experience cardiac arrest can experience HIE.

Signs and Symptoms of Hypoxic-Ischemic Encephalopathy (HIE)

HIE has three stages, and its symptoms depend upon the stage as well as the areas of the brain that were affected. Doctors diagnose HIE based upon these signs and symptoms and with medical diagnostic tools such as magnetic resonance imaging (MRI), electroencephalogram (EEG), and monitoring of the cord blood gas levels.

The first stage is mild hypoxic-ischemic encephalopathy. Mild HIE will typically resolve itself within 24 hours to a few days without any long-lasting effects. In mild HIE, the baby is stiff and seems hyper-alert. Deep tendon reflexes might be brisk and muscle tone slightly decreased. Alternatively, the baby may be floppy and unreactive to sights or sounds. The baby may also exhibit behavioral abnormalities such as irritability, poor feeding, or excessive crying or sleepiness, often in an alternating pattern.

The second stage is moderate HIE. With moderate HIE, the infant is lethargic and may have sluggish — or nonexistent — sucking and grasping reflexes and may experience apnea and seizures within the first 24 hours after birth. The outcome of stage 2 HIE is highly variable. Some infants with moderate HIE will recover completely within a few weeks. However, others may experience permanent consequences.

The third stage is severe HIE. A stupor or coma is typical in this stage, and the infant may fail to respond to physical stimuli. Breathing may be irregular, and the infant may require a ventilator. They may experience extreme hypotonia (decreased muscle tone). In addition, the infant may lack reflexes such as sucking, swallowing, or grasping and demonstrate eye motion disturbances and dilated pupils. Infants with severe HIE may experience delayed and severe seizures that resist conventional treatments, as well as heart rate and blood pressure irregularities. Cardiorespiratory failure, often fatal, can occur.

Effects of Hypoxic-Ischemic Encephalopathy (HIE)

The long-term effects of hypoxic-ischemic encephalopathy can be severe and result in permanent health problems. In fact, HIE due to fetal or neonatal asphyxia is a leading cause of death or severe impairment among infants. Multiple peer-reviewed studies have noted that by age 2, “up to 60% of infants with HIE will die or have severe disabilities, including mental retardation, epilepsy, and cerebral palsy.”

According to an article published in Medscape in 2018, as many as 80% of infants who survive severe HIE develop serious complications. Between 10% and 20% develop moderately serious disabilities, and as many as 10% are healthy. Among the infants who survive moderately severe HIE, 30% to 50% may have serious long-term complications, and 10% to 20% have minor neurologic morbidities.

HIE, especially severe HIE, can involve multiple organs, such as the heart, lungs, and liver. In infants who survive severe HIE, the heart is affected 43% to 78% of the time, the lungs, 71% to 86% of the time, the renal system, 46% to 72% of the time, and the liver, 80% to 85% of the time.

In addition, infants with HIE can experience developmental and motor-skill delays, cerebral palsy, cognitive problems, epilepsy, and vision and hearing loss.

Developmental Delays

A developmental delay is characterized by a child missing a physical, mental, or emotional milestone or falling behind their peers. Alternatively, developmental delays can manifest as the child’s progression through these phases slowing, stopping, or reversing.

These can impact vision, motor skills, language or speech, social or emotional skills, or cognitive thinking. If a child experiences delays in more than one of these areas, it can be classified as a global development delay.

Cerebral Palsy

Cerebral palsy is a broad term for a group of disorders that affect a person’s ability to move, maintain balance and posture, or speak. Cerebral palsy may not be evident at birth but may be diagnosed after a child fails to meet typical milestones for their age. At least 9% of cerebral palsy cases are the direct result of HIE, and HIE may indirectly cause others. Two or three children out of every 1,000 have cerebral palsy. In severe cases, children with cerebral palsy are paralyzed. While cerebral palsy is incurable, it can be treated.


Medications can help treat pain and seizures, spasticity, swelling, and incontinence.

Cognitive Problems

HIE can affect cognitive development and activity. The more severe the HIE, the more severe the cognitive impairment. Infants with severe HIE have an increased risk of mental retardation. Cognitive impairment can impact the ability to learn, make decisions, and interact socially. HIE can also affect memory


HIE is one of the most frequent causes of epilepsy, which is a chronic disorder characterized by unpredictable seizures and other health problems. About 3.4 million people have epilepsy — 470,000 of which are children. Epilepsy is a spectrum condition with many seizure types that vary from person to person. Seizures can affect a person’s work and relationships.y.

Vision and Hearing Loss

Oxygen deprivation is a common cause of cortical vision impairment, which refers to damage to the portion of the brain that processes vision. It can cause tunnel vision or strabismus, a condition in which the eyes are misaligned and point in opposite directions.

Babies with HIE are at a higher risk of sensorineural hearing loss, which occurs when the inner ear is damaged or if pathways between the brain and inner ear are damaged. It can be temporary or permanent. If sensorineural hearing loss is permanent, audiologists can treat it with hearing aids or cochlear implants.

Motor-Skill Developmental Delays

HIE can be a key factor in delays in motor-skill development. These delays may be related to HIE-induced cerebral palsy, epilepsy, or other conditions. Parents typically notice these delays when their child misses certain developmental milestones.

Treatment for Hypoxic-Ischemic Encephalopathy (HIE)

Diagnosing HIE early is vital because it can be treated. Timely treatment can lessen the severity of the condition. Short-term treatment often includes therapeutic hypothermia for 72 hours, a ventilator, and medications to treat seizures, heart rate, and blood pressure.

Neonatal hypothermia is provided in some hospital neonatal intensive care units and involves moderately reducing a patient’s body temperature to slow disease progression and improve health. Hypothermia treatment, also referred to as “cooling treatment,” has been shown to improve outcomes in people who have suffered a neurological injury, including newborns. Researchers still aren’t quite sure why lowering body temperature is beneficial, but the current theory is that a lower core temperature slows biological processes, which means that damage to tissue also occurs more slowly. After hypothermia treatment, doctors gradually rewarm the infant to normal body temperature.

According to Seattle Children’s Hospital, doctors may use other treatment options such as high-frequency ventilation, which sends small puffs of air into the child’s lungs. Babies with respiratory failure may receive nitric oxide through a breathing tube to open the blood vessels in their lungs so that the vessels can carry oxygen-rich blood around the body. Doctors sometimes use a treatment called extracorporeal membrane oxygenation (ECMO), which uses a machine outside of the body to add oxygen to the baby’s blood.

Long-term treatments are meant to help the child adapt to the symptoms caused by the brain injury and depend upon the severity of the diagnosis. These include seizure medications and therapies to support the heart and maintain healthy blood pressure functioning, dialysis, and physical and occupational therapy. 

Life After Hypoxic-Ischemic Encephalopathy (HIE)

The seriousness of a baby’s condition and the lifelong complications depend upon several factors. These include:

The length of time the baby was without oxygen

The baby's birth weight and overall health

The speed and efficiency of treatment

Parents of children with brain injuries can enhance their children’s quality of life by consulting with a medical team and following their doctors’ advice, being open to various treatment options, and taking an active role in physical and occupational therapy settings.

Finally, parents can help their children set realistic and achievable goals and celebrate their accomplishments with them. And they can offer encouragement and constructive advice for meeting unmet goals.

Many children with special needs thrive with a routine, and parents can be instrumental in establishing that routine. It’s important that parents pay attention to their own wellness, too — seeking support and counseling if needed. Taking care of a child with a birth injury can be taxing and expensive. You may need to take considerable time off work, hire a special caregiver, or quit your job entirely. You may have to spend considerable money on treatments, therapies, and education. No two injuries or children are the same. Finding the right option for your child is critical.