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PubMed This is a summary of 94 peer-reviewed journal articles Updated
Obstetrics

Understanding the Diagnosis: When the Neural Tube Does Not Close

At a Glance

A neural tube defect (NTD) occurs when the tissue that forms a baby's brain and spinal cord doesn't close fully in early pregnancy. These defects are caused by a complex mix of genetics and environmental factors, not a parent's actions. Specialized imaging and care teams help guide next steps.

Receiving a diagnosis of a neural tube defect (NTD) during a prenatal ultrasound can feel like the world has suddenly shifted. It is often a moment of profound shock and grief for parents [1]. While this news is overwhelming, it is important to understand that you are not alone, and there is a vast community of specialists and families who navigate this path every day.

What is a Neural Tube Defect?

In the very first month of pregnancy—often before a person even knows they are pregnant—the embryo develops a flat strip of tissue called the neural plate [2]. In a typical pregnancy, this plate folds over and fuses together to form a tube, which eventually becomes the brain and spinal cord [2]. This process is called neurulation [3].

A neural tube defect occurs when a portion of this tube fails to close completely [4]. Depending on where the tube stays open, it can affect the development of the brain, the skull, or the spine [5][6].

Why Did This Happen?

One of the most difficult parts of this diagnosis is the “why.” It is natural to look for a reason, but it is vital to know that most NTDs are multifactorial, meaning they are caused by a complex combination of genetics and environment that is rarely within a parent’s control [7][8].

  • Folic Acid (Vitamin B9): Folic acid is essential for helping the neural tube close [9]. Because the neural tube closes by day 28 of pregnancy, this nutrient is critical in the earliest weeks [2]. While many cases are prevented by folic acid fortification in food, some NTDs occur even when a parent takes standard prenatal vitamins [10][11]. Importantly, for any future pregnancies, clinical guidelines strongly recommend that parents with a history of an NTD pregnancy consult their doctor about taking a high-dose folic acid prescription (typically 4 mg/day) starting months before conception [12].
  • Genetics: Researchers have identified many different genes involved in neural tube closure [7]. Sometimes, a tiny change in a specific gene can increase the risk, regardless of nutrition [13].
  • Medical Conditions: Factors like maternal diabetes or obesity can influence how the embryo develops [14][15].
  • Medications: Certain medications, such as some anti-seizure drugs, are known to increase the risk of these defects [16].

The Spectrum of NTDs

Neural tube defects exist on a broad spectrum (learn more in Types and Anatomy). No two diagnoses are exactly the same, and the impact depends heavily on the location and severity of the opening.

  1. Anencephaly: This is a severe, life-limiting condition where the upper part of the neural tube does not close, resulting in the absence of a major portion of the brain and skull [5][17].
  2. Encephalocele: This occurs when a portion of the brain or its covering protrudes through an opening in the skull [4][18].
  3. Spina Bifida: This is the most common form, where the lower part of the neural tube does not close [6]. The most common type is myelomeningocele, an open defect where the spinal cord and nerves are exposed [6][19].

Three Stabilizing Facts

When you are in the “eye of the storm” after a diagnosis, these three facts can help provide a foundation for the road ahead:

01

Diagnosis & Imaging: Understanding Your Ultrasound and MRI Results

Learn how neural tube defects are diagnosed. Understand your high-resolution ultrasound, fetal MRI, and terms like Chiari II malformation and lesion level.

02

Building Your Care Team: Coordinating Your Child's Specialists

Learn how to build a multidisciplinary care team for your child with spina bifida. Discover which pediatric specialists you need and how to plan for delivery.

Common questions in this guide

What is a neural tube defect?
A neural tube defect happens when the tissue that eventually becomes the baby's brain and spinal cord fails to close completely during the first month of pregnancy. This can affect the development of the brain, skull, or spine.
Did I do something to cause my baby's neural tube defect?
No, it is not your fault. Neural tube defects are multifactorial, meaning they result from a complex combination of genetics and environmental factors that are rarely within a parent's control.
What role does folic acid play in neural tube defects?
Folic acid helps the neural tube close properly during the earliest weeks of pregnancy. While taking folic acid greatly reduces the risk, some defects can still happen even when a parent takes standard prenatal vitamins.
What are the different types of neural tube defects?
The spectrum includes spina bifida (where the lower spine doesn't close), anencephaly (a severe condition affecting the brain and skull), and encephalocele (where brain tissue protrudes through an opening in the skull).
What are the next steps after a neural tube defect is found on an ultrasound?
Your doctor will likely recommend additional imaging, such as a specialized ultrasound or a fetal MRI, to confirm the diagnosis and pinpoint the defect's exact location. You will also likely be referred to a maternal-fetal medicine specialist or fetal care center.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What specific type of neural tube defect does the ultrasound show?
  2. 2.At what level of the spine is the lesion located, and how does that affect the expected mobility?
  3. 3.Is this an 'open' or 'closed' defect, and what does that mean for our treatment options?
  4. 4.Are there any signs of hydrocephalus or other brain-related changes like the Chiari II malformation?
  5. 5.What are the next steps for confirming the diagnosis, such as an MRI or a referral to a fetal care center?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (23)
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This information is provided to help you understand a prenatal neural tube defect diagnosis and is for educational purposes only. It should not replace medical advice or guidance from your maternal-fetal medicine specialist or care team.

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