Can I get pregnant if my thyroid is underactive?

Yes, but it is more difficult to conceive. There is also a risk of miscarriage.

Can I get pregnant if my thyroid is overactive?

Yes, but it is more difficult to conceive. If the overactivity is not treated there is a chance of miscarriage and premature delivery.

I’m hypothyroid. Should I continue to take my levothyroxine during my pregnancy?

Yes, as soon as you know you are pregnant it is usually recommended that your levothyroxine is increased immediately by 25-50mcg daily. You should then contact your GP and arrange to have a thyroid blood test

I’m hyperthyroid and take carbimazole. Is this okay during pregnancy?

For hyperthyroid (overactive) patients Propylthiouracil is the medication of choice during pregnancy for the first trimester only. Carbimazole is the drug used during the rest of pregnancy. 

You should discuss your plans for pregnancy with your endocrinologist before you try to conceive as it may be necessary to change your medication, or in some cases it can be stopped.

If you are being treated with antithyroid drugs (e.g. carbimazole or Prophylthiouracil (PTU)) and you haven’t already discussed your pregnancy plans with them beforehand, you should contact your endocrinologist or GP as soon as possible after pregnancy is confirmed as it may be necessary to adjust your medication

I have been treated with radioiodine for an overactive thyroid. Will this harm the baby?

You should not get pregnant for six months after this treatment. If you are in doubt check with your GP or specialist.

I have Graves’ disease treated by surgery and am taking levothyroxine. Are there any problems for the baby?

Firstly you should increase the dose of thyroxine during pregnancy. There is also a very small chance that the baby could be born with an overactive thyroid but if so it would only last for about one month and can be treated easily. A blood test during the later part of pregnancy will indicate if there is a high risk of this.

Can I take antenatal vitamins if I have thyroid disease and take medication?

Yes, take your antenatal vitamins, but avoid taking them at the same time you take your thyroid medication. Some (calcium, for example) interfere with the absorption of thyroid medication in your system.

I’ve heard that you can develop thyroid disease after you have a baby?

Up to 9% of women can develop postpartum thyroid disease. Sometimes this is a temporary condition. It can be treated with levothyroxine.  In some cases, the thyroid disease remains a permanent condition.

Can I breast-feed my baby if I am on levothyroxine or antithyroid medication?

Yes. Breastfeeding is safe while taking levothyroxine. Breastfeeding while taking antithyroid drugs is generally safe but you should check with your endocrinologist.

Further information for patients

Pregnancy and thyroid disorders - guidance for patients

BTF Guide to Pregnancy and fertility in thyroid disorders

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