What causes HIE?
HIE has many causes and sometimes it is even impossible to determine a cause as there are so many factors. The majority of cases (research estimates 70-80%) are not preventable. It is a wonder, once you are aware of the potential causes, that any baby is born healthy with the variety of causes that can happen.
High-Risk HIE Causes
Sometimes HIE can be caused by medical situations that put someone in a "high-risk" category, such as:
- Previous c-sections where a scar could cause thinning of the uterus (rupture during VBAC can occur)
- High blood pressure such as Preeclampsia or HELPP syndrome
- Lifestyle choices such as dependency and use of alcohol, tobacco, or drug use during pregnancy can cause placental abruption
HIE from Umbilical Cord Causes
Sometimes HIE can be caused by various umbilical cord issues. Cord entanglement and compression is rare, but can occur. Sometimes a mother might notice a change in movement during pregnancy. Many of our families had "kick count saves" where movement stopped and they went into Labor and Delivery and their baby was born and resuscitated. Cord compression can happen intermittently during pregnancy or labor. HIE from too much or too little amniotic fluid, can also affect the umbilical cord leading to HIE.
Examples of cord issues include:
- Wrapped Cord: If around the neck, it is called a nuchal cord. However, the cord can sometimes be wrapped around the abdomen and limbs.
- Underdeveloped Cord: Sometimes umbilical cords do not grow correctly, either too short, or are too thin. These are hard to see on routine testing.
- True Knot: These happen when a knot forms randomly in the umbilical cord.
- Umbilical Cord Prolapse: This can happen during vaginal delivery, where the cord would deliver before the baby.
HIE from Fetal-Maternal Hemorrhage
Whether associated with a placental abruption, or just spontaneously happening, sometimes fetal-maternal hemorrhage is a cause of HIE. This occurs when a bleed happens internally and the baby and mother both lose a significant amount of blood.
HIE from Placental Issues
The placenta is a fascinating and understudied organ. It is very difficult to detect placental issues through standard imaging. There are new research studies underway through the Human Placenta Project to help understand this vital organ in hopes of catching and preventing issues, like those that can lead to HIE.
Some placental issues include placental insufficiency, where the placenta for one reason or another prematurely, or not, ages and gives out. Placental abruption is also a very common cause, but with many sub-causes. For some, they have repeat placental abruptions, for some it's lifestyle choice, and for some it's during labor and delivery. The placenta may also become clotted due to undiagnosed clotting disorders.
Placental previa can also occur where a vaginal delivery would be unsafe for the baby. Placental previa is routinely caught and a c-section is recommended if it does not move during the remainder of pregnancy.
HIE from Uterine Rupture or Other Uterine Causes
Uterine rupture is another cause of HIE. This can happen spontaneously, or due to another incident such as trauma, or during an attempt at a VBAC (vaginal birth after cesarean), where a scar could potentially cause a thinning in the uterus leading to rupture. It is highly recommended to work with a trained physician, or a high-risk physician, to determine your risk factor for birth options and repeat of issues.
HIE from Labor and Delivery
Labor and delivery is a complex process. Many factors come together for a healthy and successful birth. Sometimes, things go well, and other times they do not. Sometimes these are preventable, other times they are not.
Causes such as shoulder dystocia, where a baby gets "stuck" due to a position or a large baby, may or may not be preventable. While imaging can take a best guess at the size of a baby, many times ultrasound is inaccurate and a baby may be larger than originally predicted, or a mother's pelvic girdle is not wide enough to birth a child vaginally.
Occasionally, with the above possibilities such as cord compression, placental abruption, etc. some babies need emergency c-sections if there are distress factors that occur. Sometimes these are preventable, and sometimes they are not.
HIE from Blood Clotting Disorders
Many blood clotting disorders are not detected until something goes wrong to bring them to light, as they are not standard panels and are rare. However, many of our families have found out post-HIE that they are carriers of various blood clotting disorders such as MTHFR. More research is needed to see if there is more of connection and if certain blood tests would better screen for potential issues to the mother and child.
HIE from Post-Birth Causes
Many families have babies whose HIE was not obvious right away, or who developed HIE in post-birth situations. Some of those include:
- Breathing issues upon birth: If there are no other causes with needing to be resuscitated, sometimes babies have a harder time transitioning from inside to the outside and require ventilation. Sometimes if there is a period where breathing is unable to be started up or ventilated quickly, HIE can happen.
- Hypoglycemia or hyperglycemia: Sometimes a baby, and more common with gestational diabetes, will have a hard sugar crash. Sometimes that can cause seizures and a lack of oxygen from the crash leading to HIE.
- Meconium Aspiration Syndrome: If a baby has come into contact with the first bowel movements, which can sometimes be released during labor and delivery, they are at risk to aspirate. Meconium is thick and sticky and can case MAS. This can also lead to HIE.
- Infections: While some infections are routinely screened for such as GBS (Group B Strep), Chorioamnionitisor other bacterial infection that is undiagnosed, a baby can become septic and be at risk to develop HIE from the systemic crash that occurs.
HIE from a Cardiac Arrest or Near-SIDS Event in Childhood
Because the combination of a lack of oxygen and lack of blood flow to the brain can cause HIE, some children who experience cardiac arrest due to several different causes, or a near-SIDS event in childhood, can experience HIE. Sometimes these are near-drownings, sometimes accidental smothering during sleep, and others due to unexpected physical trauma.
Regardless of cause, Hope for HIE welcomes all families to join in our support network of over 4,700 families from around the world.