Hypoxic-ischemic encephalopathy (HIE), is a brain injury caused by a lack of oxygen-rich blood in the baby’s brain. HIE results in infant seizures, difficulty feeding, low muscle tone, limpness, organ dysfunction, and breathing problems. HIE can also lead to cerebral palsy, intraventricular hemorrhages, hydrocephalus, and learning disabilities. HIE often occurs in utero, during labor and delivery, or shortly after birth. Some causes and risk factors HIE include the:
• Nuchal cord: A nuchal cord results when the umbilical cord is looped or knotted around the baby’s neck. This limits the flow of oxygen-rich blood from the mother to the baby.
• Umbilical cord prolapse: Prolapse occurs when the umbilical cord travels through the birth canal in front of or alongside the baby. When this happens, the cord gets trapped and squeezed between the baby’s head or body and mother’s pelvis. This pressure on the cord can cause blood flow to the baby to slow down or stop.
• Preeclampsia: Preeclampsia is high blood pressure in a pregnant woman. It decreases the blood flow to the baby. High blood pressure causes damage to, or constriction of, the vessels in the placenta through where oxygenated blood normally flows.
• Post-term pregnancy: Post-term pregnancy is a name for pregnancies that extend beyond the standard 40 weeks. These pregnancies can cause HIE as the result of placental deterioration and low amniotic fluid (which happens around 37). Post-term babies may also become too large, making delivery difficult and increasing the risk of HIE.
• Chorioamnionitis and villitis: Chorioamnionitis is infection and inflammation of the placenta and fetal membranes. Villitis is an infection and inflammation of the part of the placenta involved in the exchange of oxygen and nutrients and is associated with chronic chorioamnionitis. This causes premature rupture of the membranes, which results in characteristics of prematurity such as underdeveloped lungs.
Meconium aspiration: Meconium is a mixture of amniotic fluid and the baby’s stool. Babies breath this into their lungs around the time of birth. When this happens, the baby can suffer severe respiratory distress and have breathing problems after birth.
Macrosomia and cephalopelvic disproportion: Macrosomia is a complication in which the baby is large and unable to fit through the mother’s pelvis. Labor with macrosomia is often prolonged. This is dangerous because the fetus has to withstand more contractions, which limits oxygen flow. Also, medical professionals may attempt to pull the baby out using forceps or vacuum extractors. These tools can cause trauma to the head, hemorrhages, and HIE.
Placental Abruption: This occurs when the placenta separates from the uterus, which can cause bleeding in the mother and a decreased supply of oxygen-rich blood to the baby.
Uterine Rupture: This is when the uterus tears open, potentially expelling the unborn baby out of the womb and into the mother’s abdomen. When the uterus tears, the mother may lose so much blood that the baby becomes oxygen deprived.
Malposition of the baby, such as face presentation, transverse, and breech birth: When a baby is not in the normal position, labor can be prolonged, trauma to the head can occur, and the umbilical cord can become prolapsed. These complications can cause oxygen deprivation in the baby’s brain.
Delayed emergency C-section: Often, physicians spend too much time trying to deliver a baby vaginally, and they do not move on to a C-section quickly enough, or they lack the skill or necessary equipment to promptly perform a C-section. When an indicated C-section is not performed promptly, the baby is often subject to oxygen-depriving conditions for far too long.
Severe maternal hypotension: When a mother’s blood pressure is low, the blood flowing from her, through the placenta and umbilical cord to the baby, may be insufficient. This can deprive the baby of oxygen-rich blood.
Intracranial and intraventricular hemorrhage: Hemorrhages can occur when there is trauma to the baby’s head. This can happen during labor and delivery, especially if delivery instruments such as forceps and vacuum extractors are used, or if the baby’s birth position is mismanaged. Brain bleeds can cause decreased blood flow and oxygen in the brain.
Uterine hyperstimulation: Excessively strong and frequent uterine contractions, called hyperstimulation, can result from improper use of the labor-enhancing drugs Pitocin and Cytotec. Uterine hyperstimulation pressures the vessels in the uterus and placenta, which can impede blood flow to the umbilical cord and baby. This can lead to severe oxygen deprivation and HIE.
Signs and symptoms of HIE at birth may include:
Breathing problems / need for resuscitation of the newborn.
Low APGAR Scores. An APGAR score assesses the overall health of a newborn over the first few minutes of life. It assigns scores to conditions such as the baby’s skin color and complexion, pulse rate, reflexes, muscle tone, and breathing.
Seizures shortly after birth
Difficulty feeding, including the inability to latch, suck, or swallow
Absence of other neonatal reflexes (e.g. the baby fails to respond to loud sounds or movement, does not grasp onto objects such as a finger, etc.)
Profound metabolic or mixed acidemia in an umbilical artery blood sample (the baby’s blood is acidic/has a low ph)
Hypotonia (low muscle tone/limpness)
Multiple organ problems (e.g., the involvement of the lungs, liver, heart, intestines)
Coma/altered consciousnessHIE is confirmed through tests and neuroimaging studies, including:
CT scans
PET scans
MRIs
Blood glucose tests
Umbilical cord and arterial blood gas tests
EEGs
Ultrasounds
