HIE and other related health complications like cerebral palsy, intellectual and developmental disabilities (I/DD) and seizures stem from the root cause of brain injury due to oxygen deprivation. There are many ways that a brain injury of this type can occur. In some cases, brain injury can occur due to what a layman might think is an unrelated condition. There are some cases of HIE where the cause is unknown or difficult to identify, though medical mistakes often can factor into HIE diagnoses.
HIE is sometimes a complicated diagnosis because oxygen deprivation in a baby can occur due to many different factors. In some instances, HIE may not be preventable. However, in many cases, oxygen deprivation occurs due to a health issue that medical staff missed or mismanaged during pregnancy birth or delivery. These health issues can occur in either the baby or the mother, and they need to be dealt with appropriately and quickly to prevent adverse outcomes.
What Are the Causes of and Risk Factors for HIE?
While the following is by no means a comprehensive list, it illustrates the wide variety of conditions that can cause or be risk factors for HIE. Because many of these conditions can feed into each other or (directly or indirectly) cause oxygen deprivation, it is important to get a second opinion on your child’s health status if you are concerned.
A quick note on the difference between a cause and a risk factor: a cause is a factor that directly causes a particular disease, while a risk factor is an event, substance or condition that makes it more likely that the condition will be present, but doesn’t necessarily mean that a child is guaranteed to have a particular diagnosis. Multiple risk factors can build up, however, and form a ‘causal pathway.’ These pathways occur when several risk factors align in a specific order at a specific time to make it significantly more likely that a condition will occur.
Some of the causes and risk factors for hypoxic-ischemic encephalopathy include:
High-Risk Pregnancy and HIE
Women with obesity, diabetes, high blood pressure, preeclampsia, a pregnancy involving twins, triplets or more, autoimmune disorders, and women who use alcohol or tobacco during pregnancy are considered high-risk. Women with a high-risk pregnancy are monitored differently than low-risk patients to make sure that any issues in pregnancy can be quickly addressed.
HIE from Umbilical Cord Issues
There are many things that can be concerning in regards to the umbilical cord. Because the umbilical cord is the baby’s sole source of oxygen and nutrients, it is critical that the umbilical cord function properly. If it is occluded, compressed, or knotted, this can compromise the flow of oxygen and nutrients to the baby and cause injuries.
Examples of umbilical cord issues can include:
- Nuchal Cord (when the umbilical cord is wrapped around the baby’s neck)
- Umbilical Cord Prolapse (when the umbilical cord exits the uterus before the baby does)
- Short Cord
- True Knot
- Infected or Inflamed Cord
- Vasa Previa
HIE From Placental or Uterine Complications
The umbilical cord is attached to the placenta, which is a dense network of capillary beds and oxygenated tissue that feed the baby nutrients and oxygen. Issues with the placenta have the same impact as issues with the umbilical cord – compromising the flow of oxygen and nutrients will harm the baby. Issues can include:
HIE from Uterine Rupture
In some rare cases, a mother’s uterus may tear during delivery. This can cause the baby to move into the abdominal cavity (stretching or compressing the umbilical cord) and is accompanied by massive bleeding. This can happen when a mother attempts a vaginal birth in the presence of uterine scarring (from a prior C-section, hysterotomy, myomectomy or petroplasty). This can also be accompanied by placental abruption. When massive bleeding occurs, the mother’s blood pressure may drop and decrease blood flow to the baby. This emergency situation requires a C-section delivery.
HIE from Placental Abruption
Usually, the placenta stays attached to the uterus until delivery. In a placental abruption, the placenta separates partially or completely from the uterus early. This can compromise oxygen flow to the baby since the baby’s only source of air is through the placenta and the umbilical cord. If the placenta is partially or completely detached from the uterus, air and blood flow to the baby will decrease. The severity of an abruption can vary, but a mild abruption can turn severe very quickly.
HIE from Placenta Previa
In most cases, the placenta connects to the uterus far away from the mother’s cervix. With placenta previa, however, the placenta attaches to the uterus close to the cervix, which can cause life-threatening bleeding during delivery. This condition can be detected if a mother reports on-and-off bleeding during the second half of her pregnancy; doctors should be able to diagnose this using ultrasound. In some cases, a low-lying placenta migrates out of the way as the pregnancy progresses, but if it does not, the risk of HIE can be reduced by delivering via C-section.
HIE from Placental Insufficiency
In some cases, the placenta can’t deliver enough blood to the baby. When this happens, the baby is often diagnosed with intrauterine growth restriction (IUGR) and the mother often has oligohydramnios (low amniotic fluid). Doctors should be monitoring these pregnancies closely with non-stress tests and biophysical profiles, as well as ultrasounds to measure the baby’s size, amniotic fluid levels and placental structure. They should also conduct Doppler ultrasounds to see how blood is flowing to the baby. There are usually no symptoms of insufficiency, but adequate monitoring should catch this condition.
HIE from Vasa Previa
Vasa previa occurs when the fetal blood vessels are exposed and cover the opening to the birth canal. Fetal blood vessels travel within the umbilical cord and attach to the central region of the placenta in normal uteroplacental circulation. However, when vasa previa is present, some of the fetal blood vessels travel within the fetal membranes and across the opening of the birth canal. Vasa previa can cause hypoxic-ischemic encephalopathy.
HIE from Cervical Issues
The cervix is a structure between the uterus and vagina that normally stays closed during pregnancy. If the tissue is weakened and it opens too early (cervical insufficiency), the protective membranes surrounding the baby can bulge through this opening and rupture before the baby can survive in an outside environment. In many cases, there are no symptoms, but doctors are responsible for screening for risk factors (such as prior cervical insufficiency, a history of D&C procedures, previous traumatic birth, prior premature rupture of membranes, or uterine anomalies). If a mother has risk factors, doctors should then perform a physical exam and multiple transvaginal ultrasound studies (TVS) over time to track cervix length. Doctors can help the cervix stay closed using cervical cerclage or progesterone treatment.
HIE from Oligohydramnios and Polyhydramnios
Oligohydramnios is a complication characterized by insufficient levels of amniotic fluid. Polyhydramnios is when there is too much amniotic fluid. As the baby develops, the amount of amniotic fluid tends to increase until the later parts of pregnancy, helping with nutrition and lung development. There are certain levels of amniotic fluid considered normal. If there is too much amniotic fluid, the fluid can push on the umbilical cord, compressing it and compromising blood flow. Cord compression may increase the risk of HIE if there is too little amniotic fluid as well. Risk factors for these include high blood pressure, diabetes, and placental issues. Doctors should be screening for amniotic fluid issues with physical examinations and ultrasound during the pregnancy.
HIE from Infections in the Mother or Baby
Some infections show no symptoms in the mother but can still cause HIE in the baby’s rapidly developing brain. Doctors should be gathering medical histories, conducting screens and tests for certain infections, and treating the mother so the infection doesn’t get passed to the baby during birth. In some cases, like when a mother has an active infection during delivery, it is imperative to give antibiotics and many times to deliver via C-section before the membranes rupture, so the baby is not exposed to infection via vaginal delivery. Some of these infections include:
- Chorioamnionitis and villitis
- Group B strep
- Bacterial vaginosis
- Herpes simplex virus (HSV, also known as genital herpes)
Depending on what the infection is, the baby may be diagnosed differently. The effects of neonatal infections are similar, however: infections can cause seizures, HIE, and a need for NICU admission. In many cases, adequate screening and proper prophylactic treatment (preventative measures) will prevent infection.
Diagnoses related to infection include sepsis, meningitis, encephalitis, and in some cases pneumonia. Sepsis refers to an infection that circulates through the blood and tissues, meningitis is inflammation of the membranes around the brain and spinal cord, while encephalitis is brain inflammation caused by a virus. Pneumonia is a bacterial lung infection that can cause the baby to develop breathing issues and oxygen deprivation.
HIE from Intrauterine Growth Restriction (IUGR)
There are certain ranges of weights that babies should be at specific times in the developmental process. If a baby isn’t reaching appropriate size during pregnancy, it may have IUGR. While there are numerous factors for what causes IUGR (placental issues and underlying maternal health issues among them), medical staff should be screening for IUGR with regularly-scheduled ultrasounds and other tests such as Doppler flow, weight checks, amniocentesis, non-stress tests and biophysical profiles. Proper assessment of risk factors is critical. Once diagnosed, IUGR babies must be closely monitored and delivered early, as many of them do not fare well in labor. Lack of close monitoring and timely delivery during labor can result in HIE for babies with IUGR.
HIE from Labor and Delivery Errors
There are cases where emergency interventions are needed, both in high-risk and low-risk pregnancies. During labor, unforeseen complications require prompt responses from medical teams; failure to follow proper protocols can result in HIE. Common labor and delivery errors include:
- Failing to prevent a preterm birth: Premature birth is a known risk factor for hypoxic-ischemic encephalopathy, as premature babies are not done developing yet, making their brains more fragile and susceptible to injury. There are interventions that doctors should be performing to help prevent premature birth. These interventions include:
- Using a cervical cerclage if there is cervical insufficiency.
- Treating a pregnancy with multiple gestations (twins, triplets, etc.) as a high-risk pregnancy and monitoring the pregnancy closely. Often, doctors recommend early delivery, usually via C-section, though induction can be an option as well.
- If a mother has a history of preterm birth or has risk factors for preterm birth, she can receive progesterone treatment to prolong the pregnancy. Progesterone treatment is only effective in women with a singleton pregnancy, not with twins or triplets, etc.
- Failing to prevent premature rupture of membranes (PROM): PROM occurs if a mother’s membranes rupture (‘water breaks’) more than 18 hours before labor starts. This can pose a risk for HIE and other birth injuries because the amniotic fluid that protects the baby from infection is gone. Doctors should administer antibiotics to decrease the risk of infection; in many cases, these babies need to be delivered via C-section because of the high risk of infection-related complications and umbilical cord compression issues. Doctors can also administer corticosteroids to mature the baby’s lung if they are preterm. Preventing PROM (and PPROM, which occurs together with preterm birth) means that doctors should be screening for infections. Cord compression is a serious risk with PROM.
- Prolonging a pregnancy for too long: If a baby continues to gestate for longer than 40 weeks in a post-term pregnancy, he or she can develop post-maturity syndrome. After around 37 weeks, the placenta starts to break down in preparation for delivery. Usually, this is not a problem, but if a baby gestates for too long, it can be exposed to hypoxic (low-oxygen conditions) as the placenta continues to deteriorate. Indeed, as of June 2016, the American Congress of Obstetricians and Gynecologists recommend that women be induced at 39 weeks, as waiting longer greatly increases the risk of birth injuries and hypoxic-ischemic encephalopathy.
- Prolonging labor and delivery for too long: While every pregnancy is different, and, therefore, the length of labor is different, there are certain indicators that medical personnel look for to see if labor is progressing normally. If labor is stalled, some medical interventions might be necessary to help the mother deliver the baby safely.
- Traumatic birth: The process of birth requires the baby to have mechanical force exerted on its body, as with the contractions of labor and (when a mother might need some help delivering) assistive maneuvers from medical staff. Traumatic birth occurs when a baby is injured in the birthing process. These injuries can occur to the body, tissues, organs or brain. There are many reasons why a birth might be traumatic, but some of the most common include attempts at vaginal delivery when the baby is in a face or breech position, is too big to fit through the mother’s pelvis, or has a shoulder stuck on the mother’s pelvic bones. Birth trauma can also occur due to over-strong contractions stimulated by delivery drugs, or improper technique when using a forceps or vacuum extractor, which can cause brain bleeds, skull fractures and hypoxic-ischemic encephalopathy.
- Attempting to continue a vaginal delivery when a C-section is safer: If a baby is large for its gestational age or has macrosomia, it has a higher risk of getting stuck on the mother’s pelvic bone in a condition called shoulder dystocia. If the baby is stuck or is too large to pass through the birth canal (cephalopelvic disproportion), there is a higher risk of oxygen deprivation. Some practitioners attempt to assist with a vaginal delivery using forceps or vacuum extractors, but this can increase the risk of a traumatic birth – a birth where physical force can cause bleeding, physical trauma, or fractures. There are also emergency situations where a baby has to be delivered in between 3 and 30 minutes (between decision to start C-section and the actual incision time), depending on the circumstances. Waiting longer in an emergency increases HIE risk significantly.
- Attempting a vaginal delivery when the baby is positioned in a face-first or breech position: Usually, a baby is delivered head-first. If a baby is delivered with their face pointing outward first, or feet-first, it is more likely that they will have a traumatic birth or have an umbilical cord prolapse or compression. While there are methods of attempting to shift the baby, it is often recommended that these babies be delivered via C-section.
- Attempting a vaginal birth after a history of C-section (VBAC): While in many of cases, a VBAC can be a safe experience for a mother and child, in others, a VBAC poses a heightened risk of HIE. After a C-section, uterine tissue can develop scars. These scars are points that can potentially rupture during labor, especially if mother had a classical incision or a low vertical incision. Uterine ruptures can lead to hemorrhages, and this bleeding can pose a health risk to both mother and child.
- Not properly monitoring a baby’s heart rate: It is standard practice for fetal monitoring to begin once a mother is admitted to the labor and delivery ward. This monitoring helps doctors watch the baby’s heart rate – if the baby’s heart rate drops, it may mean the baby is having fetal distress, which can lead to HIE. Monitoring requires staff to be able to recognize and properly read heart tracings; if medical personnel fail to recognize signs of distress or respond quickly enough, it is likelier that a baby will suffer HIE.
- Making mistakes in administering anesthesia: There are several medications that are commonly used in childbirth. For pain relief, women can undergo an epidural, or, in the case of C-section, anesthesia. This has risks like low blood pressure (which can compromise fetal blood flow, causing fetal distress), weaker contractions (which medical personnel compensate for using Pitocin or Cytotec), and a prolongation of labor as mothers can lose or decrease their ability to ‘bear down’ or push. All of these factors impact oxygen supply to the baby.
- Making mistakes in administering medication: Cytotec and Pitocin are often used to increase the strength of contractions and speed up labor. Both of these carry risks of hyperstimulation, where the uterus contracts too hard or too fast. In labor, blood flow to the baby decreases during a contraction and resumes when the contraction ends; most healthy babies can recover from this very well. If hyperstimulation happens, however, there is little to no time between contractions, keeping blood flow from resuming to the baby. This increases the risk of HIE. Additionally, the use of these drugs is associated with uterine rupture – if a woman has had prior C-section or other uterine surgery, the contractions can become intense enough to cause uterine rupture, which can cause hemorrhaging that compromises blood flow to the baby.
HIE from Neonatal Health Mismanagement
Babies can develop health issues after birth that require proper intervention. If intervention is done incorrectly, or is delayed, the impact of these health issues can become much worse. In many cases, however, these complications can be avoided with proper monitoring and adherence to standards of care. These health problems include:
- Neonatal breathing problems: Babies who have gone through a difficult birth can sometimes need help breathing. If they are born not breathing at all, they are resuscitated, first with positive pressure ventilation (PPV), and then, if the procedure is not successful, with several alternatives in an attempt to get the baby breathing again. If resuscitation does not work, they are placed on a breathing machine called a ventilator. Medical staff must be able to place the tube properly, or they risk the baby not having air delivered to the lungs at all, along with stomach tears and lung collapse. Medical staff also have to regulate the pressure of the gases being passed into the baby’s lungs or the baby can be at risk of the lungs getting too distended and injured to work (pneumothorax). This type of lung injury can severely impact the baby’s ability to deliver oxygen to its tissues. Blood acidity and oxygen saturation are important metrics, as low pH and low oxygen saturation can indicate that the baby is still not getting enough air. These are indicators that the ventilator is over-ventilating (removing too much carbon dioxide from the baby’s blood). This can cause lung collapse and hypocarbia (low CO2 levels), which in turn cause HIE and an injury called periventricular leukomalacia (where the baby’s brain tissue starts to die and ‘soften’ around the periventricular area). This can in turn cause brain bleeds and fluid leakage into the ventricles (hydrocephalus), where cerebrospinal fluid leaks into the ventricles, enlarging them and interfering with the development of the cerebral cortex. This impairs the development of the growth of the cerebral cortex, a key part of the brain needed for memory, attention, cognition, thought, and consciousness.
- Improperly treating meconium aspiration syndrome (MAS): If a baby has MAS, it is an emergency. In MAS, the baby inhales particles of his or her stool during labor, which has the potential to block airways, decrease oxygen to the baby’s brain, and cause infection and pneumonia. Babies with respiratory distress and MAS are admitted to the NICU, and are treated with some combination of airway clearance, ventilation, supplemental oxygen, surfactant therapy, steroid therapy, nitric oxide, ECMO or radiant warmer to maintain their body temperature, depending on the severity of the baby’s respiratory distress. If the baby’s MAS is not treated properly, it may suffer from HIE due to oxygen deprivation.
- Improperly treating jaundice and kernicterus: Babies can develop yellow skin, poor feeding and lethargy due to the increased concentrations of bilirubin (a product of the breakdown of red blood cells) after birth. Babies can need some help in safely removing this bilirubin, however, especially if it develops in the first 24 hours after birth or between days 3-7 of life. Medical staff place the babies under special blue lights or under a fiber optic blanket in a process called phototherapy, which helps the body safely remove the extra bilirubin. This is a noninvasive and easy treatment which should prevent jaundice from getting worse. If the bilirubin level becomes too high, exchange transfusions will be needed. If the jaundice isn’t recognized in time or the proper treatment is not given, bilirubin can cross the blood-brain barrier and cause kernicterus, a form of brain damage, which often overlaps with HIE.
- Improperly treating neonatal hypoglycemia: It is critical that babies’ blood sugar never drop too low. A baby’s developing brain depends exclusively on glucose for energy, so low blood sugar levels can cause brain cells to die, causing brain bleeds and HIE. This is one of the most common neonatal health issues, and one of the most easily solved. Hypoglycemia can occur if the baby has:
- Too much insulin (a disorder called PHHI)
- Intrauterine growth restriction (when the baby is small for their gestational age)
- Premature birth
- Abnormally high body temperature (hyperthermia)
- Abnormally high red blood cell mass (polycythemia)
- Sepsis (bloodstream infection)
- Growth hormone deficiency
- Dysfunctions in the glucose generation or breakdown pathways
- Depleted glycogen levels (due to oxygen deprivation or starvation)
If a baby is at risk for hypoglycemia or shows signs of hypoglycemia, blood glucose concentration must be determined within minutes (ideally via lab testing, but with a testing strip later confirmed with lab results if lab results cannot be processed quickly). Hypoglycemia can be solved with extra feedings of breastmilk or formula. If blood glucose levels are extremely low, the baby may also be given glucose solution via IV. Treatment can last up to a week (or until the baby can maintain normal glucose levels); it can take longer in premature babies, those with infections or those with low birth weight. Continued low glucose can require further specialized treatment.