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What is Holoprosencephaly?

Holoprosencephaly (HPE) is a condition that changes the way a baby’s brain develops. In HPE, the left and right sides of the brain do not separate like they should. The severity of HPE depends on how much of the brain separated properly. There are four main types of HPE:

  • Alobar: The most severe type. There is no separation between the left and right parts of the brain.
  • Semilobar: Some parts of the brain are separated properly.
  • Lobar: Most parts of the brain separated properly, but some small parts did not.
  • Middle Interhemispheric Variant (MIV): The mildest kind of HPE that affects a small part of the brain.

What Causes Holoprosencephaly?

The change to the baby’s brain development happens around five weeks of pregnancy. In many cases, there is nothing a parent did to cause HPE and nothing they could have done to prevent it.

There are different possible causes for Holoprosencephaly:

  • Genetic conditions: Up to three in four (75%) of babies with HPE have a genetic condition that caused it. The most common genetic change causing HPE involves having an extra chromosome, but there are a variety of other genetic changes that can cause HPE.
  • Maternal diabetes: Mothers with diabetes before pregnancy (type 1 or type 2) have a higher chance of having a baby with HPE (about one in 100, or 1%).
  • Unknown: Sometimes, we do not know what causes HPE.

How is Holoprosencephaly Diagnosed?

HPE is often first seen on an ultrasound of the baby. The right and left sides of the brain may look different than expected. There might also be differences in the baby’s eyes or nose. MRI can be used to get a more detailed look at the baby’s brain and face, as well as check on the other parts of the body. An ultrasound of the baby’s heart (called an echocardiogram) may be recommended because babies with HPE have a higher chance of having heart problems.

Genetic testing may be recommended to look for a cause of the baby’s HPE. This can be done by testing the amniotic fluid during pregnancy (called an “amniocentesis”) or using a blood sample from the baby after they are born.

What Else Can Be Seen with Holoprosencephaly?

About half of babies with HPE can have problems in other parts of their body such as the genitals or urinary tract, fingers or toes, spine, and heart. Babies with genetic syndromes are more likely to have other health problems. HPE might also cause changes in the appearance of the face. These changes can be mild or severe. Some examples include a cleft lip and/or cleft palate, eyes that are closer together or further apart than usual, and a small or missing nose.

What Does and Evaluation for Holoprosencephaly Look Like at Cincinnati Children’s Fetal Care Center?

An evaluation for HPE usually involves two days of appointments.

  • On day one, the MRI, ultrasound and fetal echocardiogram are done. In some cases, not all testing can be done on day one. It will be done on day two.
  • On day two, the patient and their support person will meet with a nurse coordinator, a social worker, and a genetic counselor. In the afternoon, a team meeting will be held with several specialists present. The specialists may include maternal fetal medicine, neonatology, neurology, and genetics. The team will share images from the MRI and ultrasound and talk about the diagnosis.
  • Our team is here to support patients through the process and give them the information they need to make the best decisions for them and their baby.

    What is the Long-Term Outlook for Holoprosencephaly?

    A baby’s health after birth depends on the type of their HPE. Many babies with alobar HPE do not survive very long after birth, but some can live for months to years. HPE increases the chance for breathing problems. In some cases, the breathing problems can be treated (for example, with extra oxygen). In other cases, the breathing problems may be life-threatening.

    People with milder HPE can survive into adulthood. They might have other symptoms, such as seizures, fluid buildup in the brain, feeding problems, and / or hormone problems. People with genetic conditions that caused their HPE may have other symptoms related to their genetic condition. If a person with HPE develops any additional health problems, their healthcare team can develop a treatment plan that is best for them.

    Most children with HPE have some learning problems. Children with severe HPE may not learn to walk and talk. Children with milder HPE may take longer to learn these things but will learn them at their own pace. Therapies (like speech, occupational, and physical therapies) may help children with HPE reach developmental milestones.

    What Are My Care Options For Holoprosencephaly?

    The symptoms and treatments might be difficult for your baby and your family. You can choose to focus on treatments that will keep your baby comfortable, instead of treatments to extend their life. This is called “comfort care.” If you choose comfort care or would like more information about it, our team can talk with you about how to keep your baby comfortable while you spend time with them after they are born. After learning about the diagnosis of HPE and the many difficulties that it can cause for the baby, families can choose to continue or to end their pregnancy. Both are decisions made by loving parents. We can help discuss these options and we will support your decision. For those who continue the pregnancy, parents often consider what “quality of life” means to them and what treatment options would best support this.

    Last Updated 06/2022

    Reviewed By Leandra Tolusso, MS, LGC

    Who treats this.

    The Cincinnati Children's Fetal Care Center specializes in treating complex and rare fetal conditions.