Is Anencephaly hereditary?

TL;DR: Anencephaly is a multifactorial condition, meaning it is not strictly hereditary in a simple Mendelian sense, but rather results from a complex interplay of genetic predispositions and environmental factors. While it is rarely caused by a single gene mutation, families who have had a pregnancy affected by anencephaly have an increased recurrence risk of approximately 3% to 5% in future pregnancies.

Is anencephaly considered a hereditary condition?

Anencephaly is generally classified as a multifactorial neural tube defect (NTD). This means it is not typically inherited through a single gene in an autosomal or X-linked pattern. Instead, anencephaly arises from a combination of polygenic susceptibility—where multiple small genetic variations interact—and environmental triggers. Because it is not a simple genetic disorder, most cases of anencephaly occur as isolated, sporadic events in families with no prior history of the condition.

What factors contribute to the development of anencephaly?

While the exact cause is often unknown, research indicates that the risk of anencephaly is influenced by both genetic and external factors. The following elements are known to play a significant role in the development of anencephaly:

• Folic Acid Deficiency: Low levels of folate (Vitamin B9) in the mother during the early weeks of pregnancy significantly increase the risk.


• Maternal Health: Conditions such as pre-gestational diabetes and obesity are associated with a higher incidence of neural tube defects.


• Medications: Certain anti-seizure medications taken during the first trimester can interfere with folate metabolism.


• Genetic Predisposition: Variations in genes involved in folate metabolism (such as the MTHFR gene) may contribute to an individual's susceptibility.

What is the role of genetic counseling and testing?

For families who have experienced anencephaly, genetic counseling is highly recommended before planning a future pregnancy. A counselor can help assess personal risk factors and discuss strategies to reduce the likelihood of recurrence. While there is no standard "genetic test" to diagnose anencephaly itself, prenatal screening—such as maternal serum alpha-fetoprotein (MSAFP) testing and high-resolution fetal ultrasound—is effective for early detection. In cases of anencephaly, these screenings are typically performed between 16 and 20 weeks of gestation.

Next steps

• Consult with a board-certified genetic counselor to review your family history and recurrence risks.


• Speak with an obstetrician about high-dose folic acid supplementation if you are planning a pregnancy.


• Visit DiseaseMaps.org to connect with the 31 community members who have shared their experiences with anencephaly.


• Review resources from the NIH Genetic and Rare Diseases Information Center (GARD) for the latest clinical guidelines.

Medical disclaimer: This information is for educational purposes only and should not replace professional medical advice, diagnosis, or treatment from a qualified healthcare provider.

References

• NIH Genetic and Rare Diseases Information Center (GARD): Anencephaly Overview.


• Orphanet: Neural tube defects, including anencephaly.


• OMIM (Online Mendelian Inheritance in Man): Entry for Anencephaly.


• Centers for Disease Control and Prevention (CDC): Facts about Anencephaly.