Hypoxic Ischemic Encephalopathy: Causes and Symptoms

What is hypoxic ischemic encephalopathy?

Hypoxic ischemic encephalopathy (HIE) is a type of brain dysfunction (brain injury) that occurs when the brain experiences a decrease in oxygen or blood flow. HIE can occur before birth, during labor and delivery or after birth. The amount of time the brain spends without oxygen or blood flow can impact how severely the brain is damaged.

Children who experience HIE may have no long-term consequences. Some can have mild to moderate effects from HIE, while others can have more severe disability. Brain injury from HIE can cause developmental delay, cognitive impairment, cerebral palsy (a disorder that affects the ability to move and maintain balance and posture) or epilepsy (a type of seizure disorder). The effects of HIE can become more noticeable as a baby develops. Sometimes, issues are not identified until school-age.

What are signs and symptoms of HIE?

• Decreased alertness and activity, although some babies may be more alert and react more to stimulation than a baby without HIE
• Lack of typical reflexes
• Abnormal (not typical) movements or seizures
• Low or high muscle tone
• Breathing problems

Some babies with HIE may not show signs of brain dysfunction immediately. This can occur when the event leading to a decrease in oxygen or blood flow happens before labor/delivery.

What causes HIE?

HIE can occur at any point during pregnancy, labor/delivery and after birth.

Causes during pregnancy

• Issues with blood flow to the placenta (an organ that develops during pregnancy that delivers oxygen and nutrients to the baby)
• Preeclampsia (high blood pressure and associated signs/symptoms in a pregnant person)
• Heart disease
• Problems with lung formation
• Congenital (present at birth) infections
• Low blood count (anemia) in the fetus
• If the birthing parent has substance use disorder

Causes during the labor and delivery period

• Bleeding from the placenta (including abruption, or tearing, of the placenta)
• Low blood pressure in the birthing parent
• Umbilical cord problems
• Rupture of the uterus

Causes in the postnatal period

• Severe lung or heart disease
• Major infection
• Low blood pressure in the baby
• Respiratory failure or cardiac arrest (when the baby’s heart doesn’t beat normally)

Rev. 4/2022. Mass General Brigham for Children and Massachusetts General Hospital do not endorse any of the brands listed on this handout. This handout is intended to provide health information so that you can be better informed. It is not a substitute for medical advice and should not be used to treat any medical conditions.