Spina bifida - Causes of spina bifida

The causes of spina bifida (myelomeningocele) are unknown, although a number of risk factors have been identified.

These are described below.

Folic acid

Not having enough folic acid during pregnancy is the most significant risk factor for spina bifida. Folic acid is a vitamin that occurs naturally in some foods, such as broccoli, peas and brown rice. It is also added to foods, such as some breakfast cereals and folic acid tablets are available from pharmacies, supermarkets and health stores.

It is estimated that taking a folic acid supplement before you conceive and while you are pregnant can prevent up to seven out of 10 cases of neural tube defects, such as spina bifida.

Exactly how folic acid helps prevent spina bifida is still uncertain. It may affect how the cells and tissue form in the developing baby.

Read preventing spina bifida for more information and advice about folic acid and folic acid supplements.

Family history

Having a family member with a neural tube defect, such as spina bifida, increases your chances of having a baby with spina bifida.

Also, if you have previously had a child with spina bifida, your risk of having other children with the condition is significantly increased. There is about a one in 20 chance that other children you have will also have the condition.

Medication

Some types of medicine have been linked to an increased risk of spina bifida or other birth defects, including:

• valproate
• carbamazepine
• lamotrigine

These medicines are used to treat epilepsy and some mood disorders, such as bipolar disorder.

Valproate causes neural tube defects, such as spina bifida, in one or two out of 100 cases. Exact figures for carbamazepine and lamotrigine are unknown but, due to the increased risk, it is recommended that sexually active women who are taking these medicines always use contraception.

If you are taking a medicine that increases the risk of spina bifida and you are planning a pregnancy, speak to your treatment team. Alternative medications may be available or it may be possible to change your dose. Taking extra folic acid supplements may also help minimise the risk.

You should never stop taking a prescribed medication unless advised to do so by your GP or another qualified healthcare professional responsible for your care.

Diabetes

Women with diabetes have an increased risk of giving birth to a child with spina bifida. This may be due to the excess glucose in the blood interfering with the child’s development.

Obesity

Women who are obese are at increased risk of giving birth to a child with spina bifida. Obese means that you have a body mass index (BMI) of 30 or more.

The more obese you are, the higher the risk. Severely obese women with a BMI of over 40 are thought to be three times more likely to give birth to a child with spina bifida than women who are a healthy weight.

You can use the healthy weight calculator to work out your BMI.