What are neural tube defects?

During the first month of life, an embryo (developing baby) grows a primitive tissue structure called the ‘neural tube’. As the embryo develops, the neural tube begins to change into a more complicated structure of bones, tissue and nerves that will eventually form the spine and nervous system.

However, in cases of spina bifida, something goes wrong with the development of the neural tube and the spinal column (the ridge of bone that surrounds and protects the nerves) does not fully close. Spina bifida is a Latin term that means ‘split spine’.

The chance that a pregnancy will be affected by a neural tube defect is less than one in 1,000.

What causes neural tube defects?

The cause of neural tube defects is not certain, but it appears to be due to a combination of genetic and environmental factors.

Women are at increased risk of having a baby with a neural tube defect if:

• they have already had a baby with a neural tube defect
• they or their partner have a close relative born with a neural tube defect
• they have type 1 (insulin dependent) diabetes (not gestational diabetes)
• they are obese, or take certain anti-epileptic medications, especially those containing sodium valproate or valproic acid

Prevention

About 2 in 3 neural tube defects can be prevented through increasing folate (folic acid) intake at least a month before pregnancy and during the first 3 months of pregnancy. Adequate folate levels are critical during the early days of the developing embryo, particularly the 3rd and 4th week, the period in which neural tube defects occur and when many women won't know they are pregnant.

You can increase your folate intake by eating folate-rich foods, including folate-fortified foods in your daily diet, or by taking a folic acid supplement. Good sources of folate include green leafy vegetables, fruit (citrus, berries and bananas), legumes and some cereals (bread and many breakfast cereals now have added folate).

Women who take medicines to control epilepsy, seizures or psychiatric disorders should talk to their doctor before taking folate because it can interfere with how their medications work.

For more information see folate and pregnancy.

Diagnosis

Neural tube defects may be diagnosed during the ultrasound scan that is carried out around week 12 of the pregnancy or, more likely, during the anomaly scan that is carried out at around weeks 18 to 20.

Ultrasound scans

An ultrasound scan is a safe procedure that uses sound waves to create an image of the inside of your body. Most hospitals will offer women at least 2 ultrasound scans during their pregnancy. The first is usually at around 8 to 14 weeks and is sometimes called the ‘dating scan’ because it can help to determine when the baby is due. This first scan may be able to detect problems with your baby’s spine that could indicate spina bifida if the condition is severe. If a dating scan is done earlier than 12 weeks, another ultrasound called the nuchal translucency scan is done at 12 weeks to check amongst other things for signs of Down Syndrome, and if a dating scan is not done prior to this then this scan can be used as the dating scan.

Morphology scan

The morphology or anomaly scan is an ultrasound scan that is carried out around weeks 18 to 20 of your pregnancy. This scan aims to identify any physical problems with your baby. It is usually during this scan that spina bifida is diagnosed.

Coping with the results

If tests confirm that your baby has spina bifida, the implications will be fully discussed with you. You will need to consider your options carefully. Your options are to:

• continue with your pregnancy while getting information and advice so that you are prepared for caring for your baby
• end your pregnancy

If you are considering ending your pregnancy, you should talk to your doctor or midwife. They will be able to provide you with important information and advice.

Your options for ending your pregnancy will depend on how many weeks pregnant you are when you make the decision. If you decide to end your pregnancy, you may wish to talk to a counsellor afterwards. Your doctor or midwife will be able to arrange this for you.

Call Pregnancy, Birth and Baby on 1800 882 436 to discuss your options regarding your pregnancy with a maternal child health nurse.