What Are Neural Tube Defects?

The neural tube is the structure that develops into the brain and spinal cord during the earliest weeks of pregnancy. It typically closes completely by day 28 after conception, which is often before a positive pregnancy test. When the neural tube does not close properly, the result is a neural tube defect (NTD).

Neural tube defects affect approximately 1 in every 1,000 pregnancies in the United States. They are among the most common structural birth defects, and they are also among the most preventable.

Types of Neural Tube Defects

Spina Bifida

Spina bifida occurs when the spinal portion of the neural tube does not close completely. There are several forms, ranging from very mild to more significant:

  • Spina bifida occulta: The mildest form. A small gap exists in the spine, but the spinal cord and nerves are typically unaffected. Many people with occulta never know they have it. It is often found incidentally on an X-ray taken for another reason.
  • Meningocele: The protective membranes around the spinal cord (meninges) push through the opening in the spine, forming a fluid-filled sac. The spinal cord itself is usually not involved, and surgical repair typically has good outcomes.
  • Myelomeningocele: The most significant form. The spinal canal is open along several vertebrae, and a portion of the spinal cord and nerves protrude through the opening. This form can affect mobility, bladder and bowel function, and sometimes cognitive development, depending on the location and severity of the opening.

Anencephaly

Anencephaly occurs when the upper portion of the neural tube does not close, resulting in the brain and skull not developing fully. This is a condition incompatible with sustained life outside the womb. Most pregnancies with anencephaly end in stillbirth, and babies born alive typically survive only hours to days. Receiving this diagnosis is profoundly difficult, and families deserve compassionate, individualized support as they navigate their options.

Prevention: The Power of Folate

Folate (vitamin B9) is the most effective known tool for preventing neural tube defects. Research consistently shows that adequate folate intake before conception and during the first weeks of pregnancy reduces the risk of NTDs by 50% to 70%.

How Much and When

  • The recommended daily intake is 400 micrograms (mcg) of folic acid for anyone who could become pregnant
  • People with a history of a previous NTD-affected pregnancy, certain medications (like anti-seizure drugs), or specific genetic variants may be advised to take 4,000 mcg (4 mg) daily, starting at least one month before conception
  • Because the neural tube closes so early, preconception supplementation is ideal. By the time most people realize they are pregnant, the critical window may have already passed

Food Sources

Folate occurs naturally in:

  • Dark leafy greens (spinach, kale, romaine)
  • Legumes (lentils, black beans, chickpeas)
  • Asparagus, broccoli, and Brussels sprouts
  • Citrus fruits and avocado

In the United States, enriched grain products (bread, cereal, pasta) are fortified with folic acid by federal mandate. This policy, implemented in 1998, reduced NTD rates by approximately 28%.

Even with a folate-rich diet, a daily prenatal vitamin with folic acid provides an important safety net.

How Neural Tube Defects Are Detected

Blood Screening

The maternal serum alpha-fetoprotein (AFP) test, drawn between 15 and 20 weeks of pregnancy, measures a protein produced by the fetal liver. Elevated AFP levels can indicate a neural tube defect, though false positives do occur. An elevated result prompts further evaluation, not an immediate diagnosis.

Anatomy Scan

The anatomy ultrasound at 18 to 22 weeks can visualize spinal abnormalities and certain cranial markers associated with NTDs. Advanced imaging techniques have significantly improved prenatal detection rates.

Amniocentesis

If screening suggests an NTD, amniocentesis can measure AFP and acetylcholinesterase levels in the amniotic fluid, providing a more definitive assessment.

Treatment: What Is Possible Today

Fetal Surgery for Myelomeningocele

One of the most significant advances in NTD treatment is fetal surgery. The landmark MOMS (Management of Myelomeningocele Study) trial demonstrated that prenatal repair of myelomeningocele, performed around 23 to 26 weeks of pregnancy, can reduce the need for shunting to manage fluid buildup in the brain and improve motor function compared to postnatal repair.

Fetal surgery is not appropriate for every case, and it carries its own risks, including preterm birth. It is performed at specialized centers by highly trained teams. If your baby is diagnosed with myelomeningocele, a referral to a fetal surgery center for evaluation can help you understand whether this option is available to you.

Postnatal Care

Babies born with myelomeningocele typically undergo surgical closure of the opening within the first few days of life. Ongoing care may include:

  • Physical and occupational therapy
  • Urology and bowel management support
  • Orthopedic monitoring
  • Neurosurgical follow-up if a shunt is placed

Many people with spina bifida live rich, full, and active lives. Advances in surgical technique, rehabilitation, and assistive technology continue to improve outcomes and independence.

Finding Prenatal Care on BAABY

If you are navigating a neural tube defect diagnosis or want to ensure your prenatal care includes the right screening and supplementation guidance, BAABY's provider directory can help you find OB-GYNs and maternal-fetal medicine specialists in your area who can provide expert, compassionate support.