Understanding HIE Grades: Mild, Moderate, and Severe Hypoxic-Ischemic Encephalopathy

When your baby is diagnosed with hypoxic-ischemic encephalopathy (HIE), one of the first things doctors will assess is the severity of the brain injury. HIE grades—classified as mild, moderate, or severe—help medical professionals determine the extent of oxygen deprivation your child experienced and guide treatment decisions. Understanding these grades can help you comprehend your baby’s diagnosis, anticipate the level of care needed, and make informed decisions about your child’s future. For many families, learning about HIE severity is the first step toward understanding whether preventable medical errors played a role in their child’s injury.

If your baby was diagnosed with HIE and you believe medical negligence during labor or delivery contributed to the oxygen deprivation, you may have legal options. A birth injury attorney can review your medical records at no cost and help you determine whether malpractice occurred. Because statute of limitations deadlines apply to birth injury cases, it’s important to get answers sooner rather than later. Contact a birth injury lawyer today for a free, confidential case evaluation.

On this page:

• What are HIE grades
• How doctors determine HIE severity
• Mild HIE (Stage 1)
• Moderate HIE (Stage 2)
• Severe HIE (Stage 3)
• HIE grading systems explained
• Long-term outcomes by severity
• Treatment approaches for different grades
• When HIE is caused by medical malpractice
• Getting legal help for your family
• Frequently asked questions

What Are HIE Grades?

HIE grades refer to the classification system doctors use to categorize the severity of hypoxic-ischemic encephalopathy in newborns. This brain injury occurs when a baby’s brain doesn’t receive enough oxygen (hypoxia) and blood flow (ischemia) during or near the time of birth. The grading system helps healthcare providers assess the extent of neurological damage, predict potential outcomes, and determine the most appropriate treatment approach.

Most hospitals use a three-tier classification system based on clinical criteria established by Sarnat and Sarnat in 1976, though some facilities may use modified versions or alternative grading methods. These classifications—mild, moderate, and severe (or Stage 1, Stage 2, and Stage 3)—are determined through careful neurological examination of the infant within the first hours and days after birth.

The grade assigned to your baby’s HIE diagnosis isn’t just a label. It provides critical information about the level of brain injury, helps predict developmental outcomes, and influences treatment decisions, including whether your child qualifies for therapeutic hypothermia (cooling therapy).

Understanding your baby’s HIE grade can feel overwhelming, but it gives you important context for the care your child will need and the prognosis you can expect.

How Doctors Determine HIE Severity

Medical professionals assess HIE severity using multiple clinical indicators observed during the first few days after birth. The evaluation is comprehensive and considers various neurological signs rather than relying on a single test result.

Doctors examine the baby’s level of consciousness, muscle tone, primitive reflexes, respiratory effort, and presence of seizures. They also review Apgar scores from birth, umbilical cord blood gas results, and any resuscitation efforts required in the delivery room. Brain imaging through MRI or CT scans may reveal patterns of injury that correspond with specific severity levels, though imaging findings sometimes lag behind clinical symptoms.

The timing of the assessment matters significantly. Some symptoms evolve over the first 24 to 72 hours after birth, which is why doctors may monitor your baby closely before assigning a definitive grade. A baby who initially appears to have mild symptoms might progress to moderate severity if seizures develop or consciousness declines.

Electroencephalography (EEG) monitoring helps detect seizure activity, which can indicate more serious brain injury. Continuous EEG monitoring in the neonatal intensive care unit (NICU) provides valuable information about brain function and helps clinicians track your baby’s neurological status.

The grading process requires expertise in neonatal neurology. Experienced neonatologists and pediatric neurologists consider the complete clinical picture when determining whether an infant has mild, moderate, or severe HIE.

Mild HIE (Stage 1): Symptoms and Prognosis

Mild HIE, also called Stage 1 HIE, represents the least serious form of hypoxic-ischemic encephalopathy. Babies with mild HIE typically show subtle neurological symptoms that may resolve within 24 to 48 hours after birth.

Clinical signs of mild HIE include hyperalertness or mild irritability, normal or slightly decreased muscle tone, and intact primitive reflexes with possible hyperactive responses. These infants usually maintain normal consciousness levels and don’t require significant respiratory support beyond what’s typical for newborns who experienced some delivery stress.

Your baby might appear jittery or have an exaggerated startle response. Feeding may be slightly difficult initially, but most infants with mild HIE can breastfeed or take bottles once they stabilize. Seizures are uncommon with Stage 1 HIE, and if they occur, they suggest the condition may be more serious than initially assessed.

The prognosis for babies with mild HIE is generally favorable. Research indicates that most children with Stage 1 HIE develop normally without significant long-term neurological impairments. Studies show that approximately 80-90% of infants with mild HIE have normal developmental outcomes.

However, “mild” doesn’t mean medical teams should dismiss the diagnosis or fail to monitor your child carefully. Even babies with mild HIE require close observation during the newborn period to ensure symptoms don’t progress. Some infants initially classified as having mild HIE may later show developmental delays or learning difficulties, though this is less common than with moderate or severe grades.

If you believe your baby’s mild HIE resulted from delayed recognition of fetal distress or inadequate response to labor complications, speaking with a birth injury attorney can help you understand whether medical malpractice during birth occurred.

Moderate HIE (Stage 2): Symptoms and Prognosis

Moderate HIE, or Stage 2 HIE, represents a more serious level of brain injury with clear neurological abnormalities that typically last several days. This is the most common severity level among babies diagnosed with HIE who receive therapeutic hypothermia.

Babies with moderate HIE show lethargy or decreased level of consciousness. They have noticeably decreased muscle tone (hypotonia), making them appear floppy when held. Primitive reflexes like the Moro reflex (startle response) and sucking reflex are diminished or absent. These infants often require respiratory support and have difficulty feeding.

Seizures occur in approximately 50-75% of babies with moderate HIE, typically beginning within the first 12 to 24 hours after birth. The seizures may be obvious (with visible jerking movements) or subtle (with only abnormal eye movements or changes in breathing patterns detectable on EEG monitoring).

Therapeutic hypothermia is the standard treatment for moderate HIE when initiated within six hours of birth. This HIE treatment involves cooling your baby’s body temperature to slow metabolic processes and reduce brain cell damage.

The prognosis for moderate HIE varies considerably depending on multiple factors, including how quickly treatment began, the specific pattern of brain injury seen on MRI, and your baby’s response to cooling therapy. Studies suggest that approximately 30-50% of infants with moderate HIE who receive appropriate treatment will develop normally, while others may experience mild to significant developmental delays or cerebral palsy.

Long-term outcomes can include motor delays, cognitive impairments, seizure disorders, visual or hearing problems, and behavioral challenges. However, each child is different, and some babies with moderate HIE surprise their medical teams with better-than-expected development.

Early intervention services, including physical therapy, occupational therapy, and speech therapy, can significantly improve outcomes for children with moderate HIE. Starting these therapies as soon as delays are identified gives your child the best opportunity for maximizing their potential.

Severe HIE (Stage 3): Symptoms and Prognosis

Severe HIE, also known as Stage 3 HIE, represents the most serious form of hypoxic-ischemic brain injury. Babies with severe HIE have profound neurological impairment from birth that requires intensive medical intervention.

Infants with Stage 3 HIE are stuporous or comatose, showing minimal or no response to stimulation. They have severely abnormal muscle tone—either very floppy (hypotonia) or rigid (hypertonia). Primitive reflexes are absent, and these babies typically cannot breathe independently, requiring mechanical ventilation.

Seizures are common with severe HIE and are often difficult to control with anti-seizure medications. The seizures may be frequent and prolonged, requiring multiple medications to manage. Some babies with severe HIE develop status epilepticus, a dangerous condition where seizure activity doesn’t stop.

Brain imaging in severe HIE cases shows extensive injury patterns affecting multiple areas of the brain. MRI findings typically reveal damage to deep brain structures including the basal ganglia and thalamus, as well as widespread injury to the cerebral cortex.

The prognosis for severe HIE is poor. Research indicates that 50-75% of babies with Stage 3 HIE either die in the newborn period or survive with significant disabilities. Those who survive typically have serious long-term impairments including spastic cerebral palsy, intellectual disability, epilepsy, and sensory impairments.

Despite cooling therapy and intensive medical care, severe HIE often results in profound developmental challenges. Children who survive severe HIE usually require lifelong care, including mobility assistance, feeding support, seizure management, and comprehensive therapeutic interventions.

Some families face the devastating decision of whether to continue life support when medical teams determine that survival will mean severe disability. These are deeply personal decisions that require compassionate medical guidance, family support, and sometimes pastoral or ethical consultation.

If your child suffered severe HIE due to preventable medical errors—such as failure to perform an emergency cesarean section when fetal distress was evident—you may be entitled to compensation for your child’s lifelong care needs. A birth injury attorney can help your family pursue the financial resources necessary to provide the extensive medical care, therapies, and support your child will require.

HIE Grading Systems Explained

While the Sarnat staging system remains the most widely used method for classifying HIE severity, medical professionals may reference other grading approaches depending on the hospital’s protocols.

The Sarnat and Sarnat classification, developed in 1976, grades HIE based on six clinical categories: level of consciousness, neuromuscular control, complex reflexes, autonomic function, presence of seizures, and EEG findings. This system was specifically designed for term infants (babies born at 37 weeks gestation or later) with HIE.

Some hospitals use a modified Sarnat system that simplifies the criteria or adjusts for variations in clinical presentation. The Thompson scoring system is another approach that assigns numerical values to clinical features and calculates a total score to determine severity. This method can be useful for tracking progression of symptoms over time.

For premature infants, grading HIE becomes more complex because typical neurological examination findings differ from those of full-term babies. Some neonatal specialists use alternative assessment tools specifically validated for preterm infants who experience hypoxic-ischemic injury.

Brain imaging, particularly MRI, provides additional grading information. Radiologists may describe injury patterns as mild, moderate, or severe based on the extent and location of damage visible on scans. The pattern of injury—whether it affects primarily the watershed zones (areas between major blood vessel territories) or the deep gray matter structures—can indicate the severity and nature of the oxygen deprivation event.

Regardless of which grading system your baby’s medical team uses, the purpose remains the same: to accurately assess the extent of brain injury, guide treatment decisions, and provide families with the most accurate prognosis information available.

Long-Term Outcomes by HIE Severity

Understanding what to expect as your child grows depends significantly on their initial HIE grade, though individual outcomes vary considerably even among children with the same severity level.

For children diagnosed with mild HIE, most reach typical developmental milestones on schedule. They usually walk, talk, and acquire skills within normal age ranges. However, some research suggests that even children with Stage 1 HIE may have slightly higher rates of learning difficulties, attention problems, or behavioral challenges when they reach school age compared to children without HIE. Regular developmental monitoring helps identify any emerging issues early.

Children with moderate HIE show the widest range of outcomes. Some develop completely normally, attending regular schools and participating in typical childhood activities without limitations. Others experience mild delays that improve with early intervention therapies. Still others develop cerebral palsy, intellectual disabilities, or epilepsy that requires ongoing management and affects their daily functioning.

Factors that influence outcomes for moderate HIE include the specific brain regions affected (visible on MRI), the severity and duration of seizures, the timing of cooling therapy, and access to comprehensive early intervention services. Children who receive therapeutic hypothermia within six hours of birth and who have less extensive injury on brain imaging tend to have better outcomes.

For children with severe HIE who survive, long-term disabilities are typically significant. Most will have cerebral palsy affecting their ability to move independently. Many have intellectual disabilities requiring specialized educational support. Epilepsy, vision impairment, hearing loss, and difficulty eating are common. These children often need assistive devices, adapted environments, and round-the-clock care.

The financial impact of caring for a child with moderate to severe HIE can be substantial. Families may face costs for ongoing therapies, specialized equipment, home modifications, special education services, and lost income when parents reduce work hours to provide care. When medical negligence causes or worsens the HIE, pursuing a birth injury lawsuit can provide resources to cover these expenses.

Treatment Approaches for Different HIE Grades

Treatment strategies for HIE vary based on severity, with more aggressive interventions required for babies with moderate and severe grades.

For mild HIE, treatment focuses primarily on supportive care and careful monitoring. Doctors observe these babies closely for 24 to 48 hours to ensure symptoms don’t worsen. If feeding difficulties occur, babies may receive temporary feeding support through a tube until they can nurse or take bottles effectively. Medical teams watch for signs of progression to more serious HIE and monitor vital signs, oxygen levels, and neurological status.

Therapeutic hypothermia is not typically used for mild HIE because the risks may outweigh the benefits for babies with minimal symptoms. However, if an infant initially appears to have mild HIE but then develops seizures or declining consciousness, doctors may reconsider cooling therapy.

For moderate HIE, therapeutic hypothermia is the standard of care. This involves cooling your baby’s body temperature to 33.5°C (92.3°F) for 72 hours, then slowly rewarming. The cooling must begin within six hours of birth to be effective. During treatment, your baby will be in the NICU with continuous monitoring, respiratory support as needed, and medications to prevent shivering.

Seizure management is critical for babies with moderate and severe HIE. Anti-seizure medications such as phenobarbital are commonly used, with additional medications added if seizures don’t respond to initial treatment. Continuous EEG monitoring helps doctors detect and treat both obvious and subtle seizures.

Babies with severe HIE require intensive supportive care including mechanical ventilation, blood pressure support with medications, careful fluid management, and treatment of any multi-organ dysfunction that may occur. Even with cooling therapy, the prognosis remains guarded for Stage 3 HIE.

After the acute newborn period, children who experienced moderate or severe HIE benefit enormously from early intervention services. Physical therapy, occupational therapy, and speech therapy can begin in infancy and continue for years, helping children reach their maximum potential despite brain injury.

When HIE Is Caused by Medical Malpractice

Not all cases of HIE result from medical negligence, but a significant percentage occur because healthcare providers failed to recognize warning signs or respond appropriately to delivery complications.

Common examples of malpractice that can lead to HIE include failure to monitor fetal heart rate appropriately during labor, failure to recognize and respond to signs of fetal distress, delayed C-section when emergency delivery was needed, improper use of forceps or vacuum extractors causing trauma, and failure to treat maternal infections that can compromise oxygen delivery to the baby.

Medical teams should continuously monitor your baby’s heart rate during labor for patterns that indicate oxygen deprivation. Non-reassuring fetal heart tracings—such as late decelerations, minimal variability, or prolonged bradycardia—require immediate intervention. When these warning signs appear, doctors must act quickly to resolve the problem or deliver the baby before brain injury occurs.

Certain labor complications increase the risk of oxygen deprivation and require heightened monitoring and readiness to intervene. These include umbilical cord complications such as cord prolapse or compression, placental abruption where the placenta separates from the uterus prematurely, uterine rupture, severe maternal blood pressure problems, and shoulder dystocia where the baby’s shoulder becomes stuck during delivery.

When medical providers fail to respond appropriately to these complications, preventable HIE can result. If your labor involved any of these risk factors and your medical team didn’t act urgently to deliver your baby, their delay may constitute negligence.

Additionally, failure to offer or provide therapeutic hypothermia to a baby who qualified for this treatment can worsen outcomes and may represent a separate instance of medical malpractice. Hospitals with labor and delivery units should have protocols in place to identify HIE candidates and initiate cooling therapy within the six-hour window.

Reviewing your medical records with a qualified birth injury attorney can help you understand whether the care you and your baby received met accepted medical standards or whether negligence played a role in your child’s HIE birth injury.

Finding a Birth Injury Lawyer

If you believe your baby’s HIE resulted from preventable medical errors, consulting with a birth injury attorney can help you understand your legal options and secure compensation for your child’s care needs.

Birth injury cases are medically and legally complex, requiring attorneys with specific experience in this area of law. Look for lawyers who regularly handle HIE and infant brain damage cases, have access to qualified medical experts who can review your records, and have a track record of successful outcomes in birth injury litigation.

Most birth injury lawyers work on a contingency fee basis, meaning you don’t pay attorney fees unless your case results in a settlement or verdict. This arrangement allows families to pursue justice without upfront legal costs during an already financially stressful time.

During your initial consultation, which is typically free, bring your child’s medical records if you have them, along with any documentation of your labor and delivery. The attorney will ask detailed questions about your pregnancy, labor complications, your baby’s condition at birth, and the diagnosis and treatment your child received.

Time limits called statutes of limitations apply to birth injury cases, and these deadlines vary by state. Some states have special provisions that extend the filing deadline for cases involving children, but waiting too long can jeopardize your ability to pursue compensation. Getting a case evaluation promptly protects your family’s legal rights.

Compensation in HIE cases can include past and future medical expenses, therapy and rehabilitation costs, special education needs, assistive devices and technology, home modifications for accessibility, lost earning capacity for your child, pain and suffering, and your own lost wages from caring for your child.

For families dealing with severe HIE, the compensation from a successful lawsuit can make the difference between accessing necessary care and struggling financially while trying to meet a disabled child’s extensive needs.

Don’t wait to explore your legal options. Contact a birth injury attorney today for a confidential, no-obligation case review to learn whether your family may be entitled to compensation.

Frequently Asked Questions About HIE Grades