Authors: Mekka Garcia, MD, NYU Grossman School of Medicine   

Alison L. Christy, MD, PhD, Providence Pediatric Neurology at St. Vincent Medical Center—Portland, Oregon  

Reviewed: September 2022 

SUMMARY

Anencephaly is a fatal birth defect. It occurs when a large part of the brain and skull is missing. It is due to incomplete closure of the upper part of the neural tube. This happens during early fetal development. The neural tube is what becomes the brain and spine.   

Some babies born with anencephaly may have a difference in their genes. Anencephaly can also be caused by:  

• Maternal vitamin deficiency 
• Infection 
• Certain medications taken during pregnancy  

It is a fatal defect with no treatment. In some cases, but not all, it can be prevented by supplementation with a vitamin called folate (folic acid, or B9). 

Disorder Overview

DESCRIPTION

Anencephaly occurs in 1 to 3 of every 10,000 births in the United States. It happens when the development of the brain and spinal cord is interrupted.  

While the brain and spinal cord are developing in a fetus, a thickened area of cells fold and come together. They create a structure called the neural tube.  

Any interruption or changes to the closure of the neural tube can result in structural abnormalities. These are called neural tube defects. Such defects happen in the first month of pregnancy. This is often before the pregnancy is identified.  

The most severe neural tube defect is an absence of the skull and most of the brain. This is called anencephaly. 

Anencephaly can be diagnosed during pregnancy. It is a deadly birth abnormality. It can lead to spontaneous miscarriage. A baby born with anencephaly will almost always die within the first week of life.  

There is no cure or treatment for anencephaly once it has been diagnosed.  

Supplementation with a vitamin called folate (folic acid, or B9) may prevent anencephaly in some cases. It may also help prevent other neural tube defects.

SIGNS AND SYMPTOMS

Early in the pregnancy, a person carrying a child with anencephaly may have a high level of alpha-fetoprotein in their blood. This is a protein. It is produced by the developing child. It can be increased when: 

• Neural tube defects are present. 

• Other conditions exist (such as Down syndrome). 

On an ultrasound, there may be more fluid than usual in the uterus. (This is called polyhydramnios.) A doctor may also see parts of the brain and skull missing on the ultrasound. Anencephaly is usually an isolated finding.

CAUSES

Anencephaly is thought to be caused by factors such as: 

• An abnormality in the genes or chromosomes 
• A deficiency of a vitamin called folate, or folic acid, early in pregnancy  
• Infection during pregnancy  
• Exposure to medications that can affect brain development  

People with previous pregnancies affected by anencephaly have a risk of recurrence with subsequent pregnancies.  

An enzyme called methylenetetrahydrofolate reductase (MTHFR) helps process folate. Variations in MTHFR can increase the risk of neural tube defects. This is due to problems with folate processing.  

However, many people have variants of MTHFR that do not increase the risk of neural tube defects.

LABORATORY INVESTIGATIONS

Anencephaly can be diagnosed with the following:

TREATMENT AND THERAPIES

There is no treatment for anencephaly.  

Neural tube defects occur early in pregnancy. So, the Centers for Disease Control and Prevention (CDC) recommends supplementation of 400 micrograms of folic acid a day for everyone with the potential to become pregnant.  

This reduces the risk of neural tube defects. A doctor may recommend a higher amount. That will depend on a person’s risk factors. Folic acid is the only type of folate shown to reduce the risk of neural tube defects.    

OUTLOOK

Anencephaly is a fatal condition. If it is detected in early pregnancy, termination of the pregnancy is usually recommended. Anencephaly is not compatible with life. Death usually occurs within a week after delivery.

RELATED DISORDERS

Conditions with similar symptoms include:

Child Neurology Foundation (CNF) solicits resources from the community to be included on this webpage through an application process. CNF reserves the right to remove entities at any time if information is deemed inappropriate or inconsistent with the mission, vision, and values of CNF. 

Research 

Currently, there are no listings for Anencephaly in ClinicalTrials.gov. Check back often and talk with your healthcare provider to identify upcoming trials.  

If you have an interest in searching for any future trials that may be starting: 

1. Go to the Home page of ClinicalTrials.gov 
2. Under “Status”, click on “Recruiting and not yet recruiting studies” 
3. Under “Condition or disease”, type Anencephaly in the field. A drop-down list will appear if this disorder is included. 
4. You can narrow the search by entering a Country name 
5. Once on the disorder page of trials, narrow your search under “Eligibility Criteria” and click “Age/Age Group/Child (birth to 17)” 

ClinicalTrials.gov is a database of privately and publicly funded clinical studies conducted around the world. This is a resource provided by the U.S. National Library of Medicine (NLM), which is an institute within the National Institutes of Health (NIH). Listing a study does not mean it has been evaluated by the U.S. Federal Government. Please read the NLM disclaimer for details.    

Before participating in a study, you are encouraged to talk to your health care provider and learn about the risks and potential benefits. 

The information in the CNF Child Neurology Disorder Directory is not intended to provide diagnosis, treatment, or medical advice and should not be considered a substitute for advice from a healthcare professional. Content provided is for informational purposes only.  CNF is not responsible for actions taken based on the information included on this webpage. Please consult with a physician or other healthcare professional regarding any medical or health related diagnosis or treatment options. 

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Mai CT, Isenburg JL, Canfield MA, Meyer RE, Correa A, Alverson CJ, Lupo PJ, Riehle-Colarusso T, Cho SJ, Aggarwal D, Kirby RS; National Birth Defects Prevention Network. National population-based estimates for major birth defects, 2010-2014. Birth Defects Res. 2019 Nov 1;111(18):1420-1435. https://doi.org/10.1002/bdr2.1589. Epub 2019 Oct 3. PMID: 31580536; PMCID: PMC7203968.  

Yuskaitis CJ, Pomeroy SL. Development of the Nervous System. In: Polin RA, Abman SH, Rowitch DH, Benitz WE, Fox WW, editors. Fetal and Neonatal Physiology. Fifth edition. Philadelphia: Elsevier; 2017. p. 1294–1313.e2.