Pregnancy risks Dr Matthew Walker While it's perfectly possible to conceive and deliver a completely healthy baby while taking anti-epileptic drugs, there are dangers. Here Dr Walker assesses the risks and the best ways to reduce them.

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Risk from seizures Risk from anti-epileptic drugs

Counter-balancing medication Breastfeeding

The blood levels of anti-epileptic drugs (AEDs) often fluctuate during pregnancy and the frequency of seizures at this time can increase or decrease.

Convulsive seizures can damage the baby in the womb or result in miscarriage, so it's essential to take your AEDs as instructed by the doctor to keep the number of seizures to a minimum.

AEDs themselves pose a small risk to the development of the baby in the womb. The overall frequency of major abnormalities of the baby at birth is approximately two per cent for the general population, six per cent for babies born to mothers on one AED, and up to 20 per cent for babies born to mothers on three different AEDs. So before getting pregnant, it's important to be on the least amount of medication that adequately controls your seizures.

The most common significant abnormality in babies born to mothers with epilepsy is cleft lip/palate. This accounts for about one-third of the abnormalities.

Spina bifida is more common in babies whose mothers take valproate (one to two per cent of births - ten times the risk in the general population) or carbamazepine (half to one per cent of births). Patients on these drugs should have ultrasound and blood tests during pregnancy to detect spina bifida early.

All women on AEDs should be given folic acid tablets before conception and throughout the first three months of pregnancy as this may reduce the risk of miscarriage and foetal abnormalities, especially spina bifida.

In the last month of pregnancy, vitamin K supplements for the mother are often advisable, and the newborn child should also receive vitamin K, as some anti-epileptic drugs decrease the amount of this vitamin in the body. Lack of vitamin K can cause result in serious bleeds into the brain at birth.

Women taking AEDs can, in almost all cases, breastfeed safely, as very little of most AEDs is passed into the milk. The exceptions are high doses of ethosuximide or phenobarbitone. In such cases, you should discuss this with your doctor.

This article was last medically reviewed by Dr Rob Hicks in October 2006.
First published in May 2002.