Pregnancy, breastfeeding and fertility while taking phenytoin

Phenytoin and pregnancy

Phenytoin has been linked to an increased risk of problems for your baby if you take it during pregnancy.

You'll usually only be advised to take it if your doctor thinks the benefits of the medicine outweigh the risks.

If you take phenytoin for epilepsy, it's important that this is controlled during pregnancy, as seizures can harm you and your baby. If you become pregnant, keep taking phenytoin, but talk to your doctor straight away. It's likely that you will need to be seen in a specialist epilepsy clinic, and they may want to change your medicine.

If you're trying to get pregnant or have become pregnant while taking phenytoin, it's recommended you take a high dose of folic acid (5mg a day). You can get this from your doctor or midwife.

Ideally, it's best to take high dose folic acid for 3 months before you start trying to get pregnant and for the first 12 weeks of pregnancy. Do not worry if you have not taken it before you get pregnant, but start taking it as soon as possible once you know that you are pregnant. It helps your baby to grow normally.

Your baby may need extra monitoring for a few days after they're born. This is because they can sometimes have withdrawal symptoms from phenytoin.

Phenytoin and breastfeeding

If your doctor or health visitor says your baby is healthy, you can take phenytoin while you're breastfeeding.

Phenytoin passes into breast milk in small amounts. Most babies do not get any side effects, but some babies might be more sleepy or not feed as well.

Taking other medicines while you're taking phenytoin might increase the chance of your baby getting these side effects, although this is still rare.

It's important to keep taking phenytoin to keep you well. Do not stop taking it without talking to your doctor. Breastfeeding will also benefit both you and your baby.

If you notice that your baby is not feeding as well as usual, seems unusually sleepy or irritable, or has a rash, or you have any other concerns about them, talk to your pharmacist, midwife, health visitor or doctor as soon as possible.

Phenytoin and fertility

There's no good evidence to suggest that taking phenytoin causes fertility problems in men or women.

However, speak to your doctor if you're female and trying to get pregnant. They may want to review your treatment.