What causes hypoxic-ischemic encephalopathy (HIE)?

Hypoxic-ischemic encephalopathy (HIE), sometimes referred to as birth asphyxia, is a neonatal brain injury caused by an insufficient flow of oxygen-rich blood. There are a variety of factors that may lead to HIE, including maternal health issues, labor and delivery complications, infections, improper fetal monitoring, or failure to provide needed intervention (such as an emergency C-section). Unfortunately, many cases of HIE are the result of negligent actions by medical professionals and organizations. When negligence causes HIE and/or other forms of harm to a patient, it constitutes medical malpractice. Parents have the option of pursuing a birth injury lawsuit to obtain the funds for their child’s medical care and other expenses associated with HIE and related disabilities (such as cerebral palsy).

On this page, we will focus on some of the most common causes and risk factors for HIE.

Timely delivery is critical

Most of the medical conditions and complications that can lead to an HIE diagnosis can be prevented with a timely delivery. Many of the following causes of HIE warrant an early, planned delivery. In other cases, urgent situations may arise that necessitate a more urgent delivery, often via emergency C-section. Research shows that when the decision to perform an emergency C-section is made, the baby should usually be delivered in five to 30 minutes, depending on the circumstances (1). A short decision-to-delivery interval is especially important when obstetrical emergencies such as umbilical cord prolapse are involved. Often, physicians spend too much time trying to deliver a baby vaginally, and they do not move on to do 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 delayed, the baby is often subject to oxygen-depriving conditions for far too long.

Risk factors and causes of HIE

Maternal health issues

Doctors should provide top-notch medical care to all expectant mothers, but may need to take special precautions when a woman has a high-risk pregnancy. There are a variety of issues that can make a pregnancy high-risk; essentially, it can be any condition that may negatively impact the health of a mother and/or baby. The following are just a few examples of high-risk pregnancy conditions that can cause or increase the risk of hypoxic-ischemic brain injury:

  • Diabetes/gestational diabetes: Both pre-existing diabetes and gestational diabetes (which occurs when a woman is diagnosed with diabetes for the first time part-way through pregnancy) can increase the baby’s risk of HIE and other birth injuries. If diabetes is diagnosed early, it can often be safely managed through dietary counseling, exercise, insulin, and other interventions (2). Proper medical management is very important because the fetus may become large for gestational age or macrosomic; these issues increase the risk of delivery complications and HIE (3, 4).
  • High blood pressure/preeclampsia: Maternal high blood pressure and preeclampsia (high blood pressure and other signs of organ dysfunction, beginning after about 20 weeks of pregnancy) both make a pregnancy high-risk (5). Among other complications, these conditions increase the risk of placental abruption, an obstetrical emergency in which the placenta becomes detached from the uterine wall before the baby is born. Placental abruption can lead to dangerous maternal bleeding and oxygen deprivation in the baby (6).
  • Maternal obesity: Obesity during pregnancy increases the risk of a number of medical complications that can threaten the health of mother and baby. Research shows that children born to obese mothers are more likely to have cerebral palsy, and that a large part of this association is due to birth asphyxia/HIE (7). Read more about that study here.
  • Multiples pregnancy: Women pregnant with twins and other multiples are at increased risk of complications that can lead to HIE. These include (among others), premature birth, umbilical cord problems, preeclampsia, and gestational diabetes (8).
  • Maternal age: Women over the age of 35 are often considered to be of “advanced maternal age” (9), although the risks associated with age increase more on a continuum basis (10). Older mothers are at a higher risk of developing conditions like preeclampsia and gestational diabetes, which in turn increase the likelihood of the baby sustaining a hypoxic-ischemic injury.

Umbilical cord issues

The umbilical cord connects a mother to her unborn baby. It is the baby’s only source of oxygen; therefore, complications involving the umbilical cord greatly increase the risk of birth asphyxia. With proper prenatal testing and fetal monitoring, these issues can often be diagnosed before HIE occurs. However, without timely diagnosis and management, the consequences can be serious. Umbilical cord issues include the following (11):

  • Umbilical cord compression: Several of the following conditions can cause cord compression.
  • Nuchal cord: When the cord is looped around the baby’s neck.  
  • True knot: When the cord becomes tied in a knot.
  • Umbilical cord prolapse: When the cord descends the birth canal before or alongside the baby.
  • Short umbilical cords: When a cord is unusually short, it is at higher risk of stretching and rupturing, and may lead to placental abruption.
  • Vasa previa: Vasa previa is a condition in which umbilical cord vessels migrate out into the amniotic sac membranes, where they are at high risk of rupturing if the baby is delivered vaginally. This condition has the potential to lead to massive fetal blood loss, but can often be managed safely with a planned C-section.
  • Chorioamnionitis: This is an infection of the fetal membranes, which can spread to the umbilical cord, placenta, fetus, and amniotic fluid.

Placental issues

There are a variety of placental complications that can dangerously deprive a baby of oxygen and cause HIE. These include:

  • Placental abruption: As already discussed, this occurs when the placenta separates prematurely from the uterine lining (12).
  • Placenta previa: This is a condition in which the placenta lies unusually low in the uterus, where it partially or completely covers the mother’s cervix and may block the baby’s passage out of the womb (13).
  • Placenta accreta:  This is a condition in which the placenta does not properly separate from the uterus during labor and delivery because it has grown too deeply into the uterine wall. If undetected and not properly treated, placenta accreta can cause severe hemorrhages, which can pose a serious health threat to both mother and child (14).
  • Placental insufficiency: If a pregnancy involves placental insufficiency, this means that the placenta is unable to supply enough oxygenated, nutrient-rich blood to the baby. Treatment for placental insufficiency may involve addressing underlying causes such as high blood pressure and diabetes. In some cases, early delivery will also be necessary (15).

Postterm pregnancy

Postterm pregnancy is a name for pregnancies that extend beyond the standard gestation time. Postterm pregnancies entail a higher risk of several complications that can lead to HIE, including placental insufficiency and large fetal size (16).

Chorioamnionitis and villitis

Chorioamnionitis is infection and inflammation of the placenta and fetal membranes. If chorioamnionitis spreads to the part of the placenta that is involved in the exchange of gases (such as oxygen) and nutrients, then it is termed villitis.  If these conditions are improperly treated, the baby may have HIE or another birth injury (17).

Meconium aspiration  

Meconium is a mixture of amniotic fluid and the baby’s stool. Sometimes, babies breathe this into their lungs around the time of birth; this is called meconium aspiration syndrome (MAS). When this happens, the baby can suffer severe respiratory distress, which can cause or contribute to oxygen deprivation and HIE. It is important to note that MAS can also be caused by oxygen deprivation/fetal distress (18).

Fetus cannot fit through birth canal

In some cases, a baby is unable to fit safely through the mother’s birth canal. This can cause prolonged and arrested labor, traumatic birth injuries, and oxygen deprivation/HIE. Fetal fit issues may stem from a variety of complications, including the following:

Sometimes, medical professionals attempt to pull the baby out using forceps or vacuum extractors. When used improperly, these tools can cause trauma to the baby’s head, brain hemorrhages, and HIE. In many cases, a C-section should be performed instead.

Uterine rupture

Uterine rupture occurs when the uterus (womb) tears open, potentially expelling the unborn baby out of the womb and into the mother’s abdomen. This most typically happens when there is a prior history of C-section or surgery to the uterus. When the uterus tears, the mother may lose so much blood that the baby becomes oxygen deprived. Alternatively, the rupture can cause the placenta and cord to be cut off from circulation, which also deprives the baby of oxygen. Women who have a vaginal birth after C-section (VBAC) are at an increased risk of uterine rupture (19).

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 and lead to HIE. Maternal hypotension can occur as a side effect of spinal anesthesia (20).

Intracranial hemorrhages

Intracranial hemorrhages (brain bleeds) 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 (such as face presentation or breech birth) is mismanaged.  Brain bleeds can cause decreased blood flow and oxygen in the brain (21).

Uterine hyperstimulation (tachysystole)

Uterine hyperstimulation (tachysystole) refers to a complication in which uterine contractions become excessively strong and frequent. This can result from improper use of the labor-enhancing drugs Pitocin and Cytotec. Uterine hyperstimulation puts too much pressure on 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 (22).

Award-winning lawyers helping children with HIE

The attorneys at ABC Law Centers: Birth Injury Lawyers (Reiter & Walsh, P.C.) have been advocating for children with hypoxic-ischemic encephalopathy (HIE) and other birth injuries since 1997. Our firm’s exclusive focus on birth injury enables us to provide unparalleled service to our clients. Our attorneys have been recognized as among the “Best Lawyers in America” by U.S. News & World Report, which also recognizes ABC Law Centers: Birth Injury Lawyers as one of the best medical malpractice law firms in the nation.

If your child experienced a birth injury and now has HIE, cerebral palsy, a seizure disorder, or any other long-term condition, please contact us today.  Our Michigan HIE lawyers are available 24/7 to speak with you.

“Jesse, Rebecca and team are fabulous lawyers. So knowledgeable and compassionate; I highly recommend them.”

-Client review from 4/18/2016

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Related resources

Video: Michigan hypoxic-ischemic encephalopathy (HIE) lawyers discuss birth asphyxia and HIE

Watch a video of partners Jesse Reiter and Rebecca Walsh talking about the causes of HIE and the groundbreaking treatment for this condition.


  1. Tashfeen, K., Patel, M., Hamdi, I. M., Al-Busaidi, I. H., & Al-Yarubi, M. N. (2017, February). Decision-to-Delivery Time Intervals in Emergency Caesarean Section Cases. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5380420/.
  2. Durnwald, C. (n.d.). Gestational diabetes mellitus: Glycemic control and maternal prognosis. Retrieved March 25, 2019, from https://www.uptodate.com/contents/gestational-diabetes-mellitus-glycemic-control-and-maternal-prognosis.
  3. Caughey, A. B. (n.d). Gestational diabetes mellitus: Obstetrical issues and management. Retrieved March 25, 2019, from https://www.uptodate.com/contents/gestational-diabetes-mellitus-obstetrical-issues-and-management.
  4. Riskin, A., & Garcia-Prats, J. A. (n.d.). Infants of women with diabetes. Retrieved March 25, 2019, from https://www.uptodate.com/contents/infants-of-women-with-diabetes
  5. August, P., MD, & Sibai, B., MD. (n.d.). Preeclampsia: Clinical features and diagnosis. Retrieved March 11, 2019, from https://www.uptodate.com/contents/preeclampsia-clinical-features-and-diagnosis
  6. August, P., & Sibai, B. M. (n.d.). Preeclampsia: Clinical features and diagnosis. Retrieved March 25, 2019, from https://www.abclawcenters.com/practice-areas/prenatal-birth-injuriesmaternal-medical-conditionsbleeding-during-pregnancy-delivery/
  7. Villamor, E., Tedroff, K., Peterson, M., Johansson, S., Neovius, M., Petersson, G., & Cnattingius, S. (2017). Association between maternal body mass index in early pregnancy and incidence of cerebral palsy. Jama, 317(9), 925-936.
  8. Women’s Health Care Physicians. (n.d.). Retrieved March 25, 2019, from https://www.acog.org/Patients/FAQs/Multiple-Pregnancy
  9. Lisonkova, S., Potts, J., Muraca, G. M., Razaz, N., Sabr, Y., Chan, W. S., & Kramer, M. S. (2017). Maternal age and severe maternal morbidity: A population-based retrospective cohort study. PLoS medicine, 14(5), e1002307.
  10. Fretts, R. C. (n.d.). Effects of advanced maternal age on pregnancy. Retrieved March 25, 2019, from https://www.uptodate.com/contents/effects-of-advanced-maternal-age-on-pregnancy
  11. Umbilical Cord Problems and Birth Injuries | ABC Law Centers: Birth Injury Lawyers. (n.d.). Retrieved March 25, 2019, from https://www.abclawcenters.com/umbilical-cord-problems/
  12. Placental Abruption: Risks, Causes, Symptoms and Treatment. (2017, May 02). Retrieved February 18, 2019, from http://americanpregnancy.org/pregnancy-complications/placental-abruption
  13. Placenta Previa: Symptoms, Causes and Treatment. (2017, May 03). Retrieved February 16, 2019, from http://americanpregnancy.org/pregnancy-complications/placenta-previa/
  14. Placenta Accreta: Symptoms, Risks and Treatment. (2017, April 04). Retrieved January 30, 2019, from http://americanpregnancy.org/pregnancy-complications/placenta-accreta/
  15. Placental insufficiency: MedlinePlus Medical Encyclopedia. (n.d.). Retrieved March 25, 2019, from https://medlineplus.gov/ency/article/001485.htm
  16. Postterm Pregnancy | ABC Law Centers: Birth Injury Lawyers. (n.d.). Retrieved March 25, 2019, from https://www.abclawcenters.com/practice-areas/prenatal-birth-injuries/maternal-medical-conditions/post-term-pregnancy/
  17. Chorioamnionitis (Maternal Infection) | ABC Law Centers: Birth Injury Lawyers. (n.d.). Retrieved March 25, 2019, from https://www.abclawcenters.com/practice-areas/prenatal-birth-injuries/maternal-infections/chorioamnionitis-and-villitis/
  18. Meconium Aspiration | ABC Law Centers: Birth Injury Lawyers. (n.d.). Retrieved from https://www.abclawcenters.com/practice-areas/neonatal-birth-injuries/meconium-aspiration-syndrome/
  19. Uterine Rupture Attorneys | ABC Law Centers: Birth Injury Lawyers. (n.d.). Retrieved March 25, 2019, from https://www.abclawcenters.com/practice-areas/prenatal-birth-injuries/labor-and-delivery-complications-and-errors/uterine-rupture-and-hie/
  20. Spinal Anesthesia and Maternal Hypotension | ABC Law Centers: Birth Injury Lawyers. (n.d.). Retrieved March 25, 2019, from https://www.abclawcenters.com/practice-areas/prenatal-birth-injuries/labor-and-delivery-medication-errors/anesthesia-mistakes/spinal-anesthesia-and-maternal-hypotension/
  21. Infant Intracranial Hemorrhages (Brain Bleeds) | ABC Law Centers: Birth Injury Lawyers. (n.d.). Retrieved March 25, 2019, from https://www.abclawcenters.com/practice-areas/prenatal-birth-injuries/traumatic-birth-injuries/intracranial-hemorrhages/
  22. Uterine Tachysystole | ABC Law Centers: Birth Injury Lawyers. (n.d.). Retrieved March 25, 2019, from https://www.abclawcenters.com/practice-areas/practice-areas-uterine-tachysystole/