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Pregnancy, breastfeeding and fertility while taking warfarin

Warfarin and pregnancy

Warfarin is not recommended during pregnancy as it can sometimes cause birth defects and bleeding problems for the baby.

However, if you have a metal heart valve you may be advised to continue taking warfarin in pregnancy because the risk of the valve clotting is greater than the risk to the baby. This would always be under the supervision of a specialist doctor.

If you are taking warfarin, it's important that you speak to your doctor before you try for a baby so that your medicine can be reviewed. They will help you weigh up the risks and benefits of staying on warfarin. It may be possible to switch to another medicine (heparin injections) before and during your pregnancy.

It's important to use reliable contraception while you're taking warfarin.

Talk to your doctor or midwife immediately if you become pregnant and you're taking warfarin. They should review you within the next working day. Do not stop taking your warfarin unless you are told to do so.

Warfarin and breastfeeding

If your doctor of midwife says your baby is healthy, it's OK to take warfarin while breastfeeding.

Warfarin gets into breast milk in tiny amounts, and it is unlikely to cause side effects in your baby.

Talk to your health visitor, midwife, pharmacist or doctor as soon as possible if:

  • your baby is not feeding as well as usual
  • your baby seems to bleed or bruise easily
  • you have any other concerns about your baby

Warfarin and fertility

There's no evidence to suggest that taking warfarin reduces fertility in either men or women.

Speak to your doctor if you're trying to get pregnant. Because warfarin is not recommend in pregnancy they will want to review your medicine.

Non-urgent advice: Tell your doctor if you're:

  • trying to get pregnant
  • pregnant
  • breastfeeding

Find out more about how warfarin can affect you and your baby on the Best Use of Medicines in Pregnancy (BUMPS) website.

Page last reviewed: 22 April 2022
Next review due: 22 April 2025