ConditionChildren's health
Neural Tube Defects
Neural tube defects (NTDs) are serious birth defects of the brain, spine or spinal cord that happen when the neural tube, the structure that becomes the brain and spinal cord, does not close completely in the first 4 weeks of pregnancy, often before a woman knows she is pregnant. The main types are spina bifida and anencephaly. Taking 400 micrograms of folic acid daily before and during early pregnancy prevents many cases. Spina bifida is treated with surgery and lifelong specialist care.
Also called: NTDs, spina bifida, anencephaly, encephalocele, myelomeningocele
At a glance
- What they are
- Birth defects from incomplete closure of the neural tube in early pregnancy.
- Main types
- Spina bifida (spine), anencephaly (brain and skull), encephalocele (brain tissue through the skull).
- Timing
- The neural tube closes by about day 28 after conception.
- Causes
- Low folate, genetics, diabetes, obesity, some anti-seizure medicines, high temperature in early pregnancy.
- Detection
- Blood screening (AFP) and ultrasound during pregnancy.
- Prevention
- 400 mcg of folic acid daily for anyone who could become pregnant; higher doses for high-risk women on medical advice.
When to get help
Call 911 or go to the ER
- A newborn with an open area on the back or head: keep it covered with a sterile, moist, non-stick dressing and get immediate specialist care
- A child with a shunt who has vomiting, severe headache, drowsiness, irritability, a bulging soft spot or seizures (possible shunt blockage)
See a doctor within a day or two
- A child with spina bifida with fever and cloudy or smelly urine
- New weakness, worsening walking, back pain or bladder changes in a child with spina bifida (possible tethered cord)
- Swallowing or breathing problems in a child with Chiari II malformation
Book a routine appointment
- Planning a pregnancy, especially with diabetes, obesity, epilepsy medicines, or a previous pregnancy with an NTD
- A raised AFP result or ultrasound finding in pregnancy, to discuss next steps
- A dimple, hair tuft or birthmark over a baby's lower spine
How neural tube defects happen
Early in development, a flat plate of cells folds into a tube that becomes the brain at one end and the spinal cord at the other. The tube normally closes by about the 28th day after conception. If any part fails to close, the brain or spinal cord and their coverings are left exposed or malformed.
Types of neural tube defects
| Type | What happens | Outlook |
|---|---|---|
| Myelomeningocele (open spina bifida) | Spinal cord and nerves bulge through an opening in the back | Lifelong disability of varying severity; most survive with treatment |
| Meningocele | Only the spinal coverings bulge out; nerves usually intact | Usually milder; surgery repairs it |
| Spina bifida occulta | Small gap in a vertebra, skin closed | Usually no symptoms; often found by chance |
| Anencephaly | Most of the brain and skull do not form | Fatal before or shortly after birth |
| Encephalocele | Brain tissue protrudes through an opening in the skull | Depends on size and location |
See spina bifida for more detail.
Causes and risk factors
Most NTDs result from a combination of genetic and environmental factors:
- Low folate before and in early pregnancy: the most important preventable factor. See folate deficiency.
- Previous pregnancy affected by an NTD, or a family history.
- Pre-existing diabetes with poor blood sugar control.
- Obesity.
- Certain medicines, especially valproate and carbamazepine for epilepsy.
- High body temperature in early pregnancy, from fever or hot tubs.
- Ethnicity: higher rates in some Hispanic populations in the US.
Effects of spina bifida
Myelomeningocele affects nerves below the level of the defect, so effects depend on the location:
- weakness or paralysis of the legs, and loss of sensation
- bladder and bowel problems, including incontinence and urinary infections
- hydrocephalus: fluid buildup in the brain in most children with myelomeningocele, often needing a shunt
- Chiari II malformation: part of the brain extends into the neck, sometimes affecting swallowing and breathing
- orthopedic problems: clubfoot, hip dislocation, scoliosis
- learning difficulties, especially with attention and executive function
- tethered spinal cord later in childhood
- latex allergy, which is more common in people with spina bifida
Diagnosis
During pregnancy
- Maternal serum alpha-fetoprotein (AFP) blood test at about 15 to 20 weeks: high levels suggest an open NTD.
- Detailed ultrasound: detects most NTDs, often from the first trimester for anencephaly and by the mid-pregnancy anatomy scan for spina bifida.
- Fetal MRI and sometimes amniocentesis for more detail.
After birth
Open defects are visible at birth. Spina bifida occulta may be suspected from a dimple, hair tuft, birthmark or fatty lump over the lower spine and confirmed with ultrasound or MRI.
Treatment
Prenatal surgery
For selected pregnancies, closing a myelomeningocele before birth, usually before 26 weeks, reduces the need for a shunt and can improve leg function, but increases risks of preterm birth. It is done at specialized fetal centers.
Surgery after birth
The opening is closed within the first days of life to prevent infection and further nerve damage. A shunt or endoscopic procedure may be needed for hydrocephalus.
Lifelong care
- urology: clean intermittent catheterization, medicines and surgery to protect kidneys and achieve continence
- bowel management programs
- physical therapy, braces, crutches or wheelchairs
- orthopedic surgery when needed
- educational support
- regular monitoring for shunt problems and tethered cord
- latex precautions
Prevention
- All women who could become pregnant should take 400 mcg of folic acid daily, starting at least 1 month before conception and continuing through early pregnancy. Most pregnancies are unplanned, so daily intake is advised for all women of reproductive age.
- Higher-risk women, such as those with a previous NTD-affected pregnancy, may be advised by their doctor to take a higher dose.
- Eat folate-rich foods and fortified grains.
- Control diabetes before conception.
- Review epilepsy medicines with a doctor before pregnancy.
- Treat fevers in early pregnancy and avoid hot tubs and saunas.
Folic acid fortification of flour and grain products in the US and many other countries has substantially reduced NTD rates.
Frequently asked questions
What causes neural tube defects?
Neural tube defects occur when the neural tube fails to close in the first month of pregnancy. Low folate is the most important preventable cause. Other risk factors include family history, diabetes, obesity, certain anti-seizure medicines and high fever in early pregnancy.
Can folic acid prevent neural tube defects?
Yes. Taking 400 mcg of folic acid daily before conception and in early pregnancy prevents a large share of neural tube defects. Women at higher risk may need a higher dose on medical advice. Because the neural tube closes so early, starting before pregnancy is important.
How are neural tube defects detected during pregnancy?
They are detected with a maternal blood test for alpha-fetoprotein at about 15 to 20 weeks and with ultrasound, which can identify anencephaly early and spina bifida at the mid-pregnancy anatomy scan. Fetal MRI can provide more detail.
Can a baby with spina bifida live a normal life?
Many people with spina bifida go to school, work, have relationships and live into adulthood. The level of disability varies widely. With surgery, bladder and bowel management, mobility aids and coordinated care, quality of life can be good.
Sources
This guide was written from current patient and clinical guidance, including:
- CDC: Folic acid, birth defects prevention; About spina bifida
- US Preventive Services Task Force: Folic acid supplementation to prevent neural tube defects
- American College of Obstetricians and Gynecologists: Neural tube defects practice bulletin
- Spina Bifida Association: About spina bifida
- NICHD: Neural tube defects