Risks of taking anti-epileptic drugs in pregnancy

Risks during pregnancy, associated with epilepsy and anti-epileptic drugs

In 1996, the UK Epilepsy and Pregnancy Register was set up to find out more about the risks associated with epilepsy and anti-epileptic drugs during pregnancy.

The results from a study of 3,607 women with epilepsy who were monitored through this register during pregnancy, whether or not they were taking AEDs, were published in a report in September 2005. The information that follows is taken from this report, because it is the most up-to-date and comprehensive information that is available at the time of writing.

The risk of AEDs affecting your unborn child appears to be greatest during the first three months of pregnancy. This is why it is advisable to speak to your doctor and get your medication reviewed before you become pregnant, if possible.

Major congenital malformations

Some of the problems that may occur in babies who are born to mothers with epilepsy are classed as major congenital malformations (MCMs).

Congenital means a condition that is present at birth. MCMs include abnormalities such as malformations of the spinal cord and spine (spina bifida), the heart (such as hole in the heart), the ribs, the bladder, the sexual organs and the fingers and toes (such as unseparated fingers).

The risks of MCMs can be related to having epilepsy itself and to any AEDs that a woman is taking during pregnancy.

• Women in the general population have a one to two per cent chance of having a baby with a MCM (one to two children in every 100 born).
• Women with epilepsy, who do not take AEDs, have a three and a half per cent chance of having a baby with a MCM.
• Women who do take AEDs have an average of around a four per cent chance of having a baby with a MCM.

The risk of MCMs also depends on the number of drugs that the woman is taking during pregnancy.

• In women who take only one AED, the average MCM rate is slightly more than three and a half per cent.
• In women who take two or more AEDs, the average risk is increased to six per cent.

Risks of major congenital malformations related to specific anti-epileptic drugs

• Carbamazepine taken as a single drug treatment (known as monotherapy) carries the lowest risk, with 2.2 babies born with MCMs in 100 women taking the drug (2.2 per cent)
• Taking sodium valproate as monotherapy at a daily dosage under 1000mg, carries a risk of 5.1 in 100 (5.1 per cent)
• Taking sodium valproate as monotherapy at daily doses over 1000mg carries a risk of 9.1 in 100 (9.1 per cent)
• Drug combinations that include sodium valproate have a significantly higher risk of MCMs than combinations that do not include this drug.
• Taking lamotrigine as monotherapy at daily dosages of 200 mg or less carries a risk of 3.2 in 100 (3.2 per cent)
• Taking lamotrigine as monotherapy at a daily dosage above 200 mg carries a risk of 5.4 in 100 (5.4 per cent)
• Taking carbamazepine and sodium valproate together carries a risk of 8.8 in 100 (8.8 per cent)
• Taking sodium valproate and lamotrigine together carries a risk of 9.6 in 100 (9.6 per cent)
• The information from the study did not include any specific data on vigabatrin, gabapentin, topiramate, tiagabine, oxcarbazepine, levetiracetam and pregabalin.

Minor congenital abnormalities

Women with epilepsy are also at an increased risk of having a baby with less severe problems, which are classed as minor congenital abnormalities. These include small fingers and toes with small nails, clubfoot and facial abnormalities. At the time of writing, there are no percentages for the risks of minor congenital abnormalities available, and more research into this is needed.

There is some evidence to show that having epilepsy slightly reduces a woman’s fertility. However, this effect is usually treatable. Having epilepsy and taking anti-epileptic drugs does not prevent a woman from receiving fertility treatment. A few women may experience a small increase in the number of seizures when taking certain hormone-based fertility drugs.

Malformation risks of anti-epileptic drugs in pregnancy: A prospective study from the UK Epilepsy and Pregnancy. J Neurol Neurosurg Psychiatry. 2005 Sep 12, sourced from http://jnnp.bmjjournals.com/cgi/rapidpdf/jnnp.2005.074203v1, 28 September 2005. 

1 November 2006

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