What is the neural tube?

The neural tube is a tube-shaped structure that forms during early pregnancy. The neural tube encloses your baby’s spinal cord and brain. The neural tube usually closes 15 to 28 days after conception, often before a woman even knows that she’s pregnant. Failure of the neural tube to close along its entire length leads to a neural tube defect at the open location.

What are neural tube defects?

Neural tube defects occur because of failure of the neural tube to fully fuse. This leads to damage and poor formation of the baby’s spinal cord and brain. A baby born with a neural tube defect usually has 1 of 3 problems:

• Anencephaly is the absence of a major part of the brain, skull and scalp.
• Encephalocele is a protrusion (bulging) of brain tissue and/or its covering membranes through a defect in the skull.
• Spina bifida is when the vertebrae (bones of the spine) that cover the spinal cord have one or more openings. This causes exposure and/or protrusion of nerve tissue and its coverings. People with spina bifida have various degrees of nerve damage.

What causes neural tube defects?

The causes of neural tube defects are uncertain. Neural tube defects are most likely caused by a combination of genetic and environmental factors. Factors that increase the risk of your baby developing a neural tube defect include not enough folic acid before and during the first 3 months of pregnancy, the use of certain medicines (for example, some epilepsy medications), maternal diabetes and genetic factors.

Can neural tube defects be prevented?

The risk of having a baby with a neural tube defect can be reduced significantly. Ensuring you get enough folic acid while you are pregnant is the best way to prevent a neural tube defect in your baby. In fact, taking folic acid supplements can reduce the risk of neural tube defects in your baby by up to 70%. Folic acid (also known as folate or vitamin B9) is in dark green vegetables, some fruits and legumes.

Since 2009, it has become mandatory in Australia for all bread making flour to be fortified with folic acid. It is recommended that all women of childbearing age get at least 0.4mg of folic acid per day. If you are planning a pregnancy, it is recommended that you take a folic acid supplement of 0.4mg at least 1 month before and 3 months after conception. If you are at increased risk of having a baby with a neural tube defect (for example, if there is a history of neural tube defect in your family), a higher daily dose of 5mg is recommended. You can get folic acid supplements over the counter at your local pharmacy.

How are neural tube defects diagnosed?

Neural tube defects can be diagnosed during your pregnancy. In the second trimester of your pregnancy, you can do a prenatal screening blood test called the second-trimester maternal serum screening test. This test helps to identify women who may have an increased risk of having a baby with neural tube defects. On its own, this test cannot diagnose neural tube defects. It gives an estimate of the chance that a pregnancy may be affected by such condition. The test may be performed between weeks 14 and 20 of your pregnancy. If a high risk screening result is found on this test or a during routine ultrasound, your doctor may offer the option to have diagnostic testing.

An ultrasound is often used to track the growth and development of your baby during pregnancy. Most cases of neural tube defects can be diagnosed by a doctor who specialises in fetal ultrasound using ultrasound between weeks 18 and 20 of pregnancy. Women with an increased risk of having a baby with neural tube defects may be offered a vaginal ultrasound at 11 weeks of pregnancy.

What will happen if my baby has a neural tube defect? Who can I discuss test results with?

If your baby is diagnosed with a neural tube defect during pregnancy, you and your partner will be referred to a specialised medical team for further assessment, information and counselling. You will meet with doctors and other health professionals who specialise in pregnancies affected by physical conditions such as this. They can explain to you the likely medical outcomes and treatment options available for your baby.

You and your partner may wish to discuss with the medical team whether to continue with your pregnancy or not. Your healthcare team are there to support you and provide relevant information to help you make this very personal decision.