Thyroid Disease and Pregnancy: Important information for women on Levothyroxine

If you have been diagnosed with thyroid disease and are taking Levothyroxine as replacement therapy, here is some important information to consider if you plan to become pregnant in the future:

Pre-pregnancy Preparation

Before attempting to conceive, it is essential to have your thyroid function tested. If you are on Levothyroxine, your GP should aim to maintain your TSH (Thyroid Stimulating Hormone) level at 2.5 mU/L or lower. If you are not on Levothyroxine, your TSH should be within the normal range.

If You Miss a Period

If you miss a period and suspect pregnancy, please take a pregnancy test.

After a Positive Pregnancy Test

1. Increase your pre-pregnancy daily dose of levothyroxine by 25 micrograms (if you do not have a 25mcg tablet, you can double your current dose on 2 days of the week and take the usual dose for the rest of the week).
2. Immediately check your thyroid function and TSI level (Thyroid Stimulating Immunoglobulin) with your GP.
3. If you are followed up by an endocrinologist, please inform your endocrinology clinic. If you are not followed up by an endocrinologist, please ask your GP to discuss with endocrinology if your thyroid function is abnormal.
4. At your pregnancy booking appointment, please inform the midwife that you have thyroid disease.

Referral to Thyroid Clinic

Monitoring during pregnancy:

1. You will need your TFTs checked at least every trimester and 6 weeks postpartum. If you have an abnormal thyroid function test, you will require more frequent monitoring, please, discuss with your doctor, or obstetric consultant or endocrinologist.
2. An acceptable TSH level in pregnancy is expected to show the following values: First trimester: 0.1-2.5mIU/L, Second trimester: 0.2-3mIU/L, Third trimester: 0.3-3mIU/L.
3. You will need to have TSI (Thyroid Stimulating Immunoglobulin) or TRAb (TSH Receptor Antibody) checked with TFTs again at 28 weeks of gestation. If this is raised, you will be referred to a neonatologist by your obstetric consultant or endocrinologist, a growth scan for your baby will be requested at 34 weeks, and a cord blood sample will be taken at time of delivery to test for your baby's thyroid function.

Keeping This Information Safe

Please keep this leaflet in a safe place for future reference and provide a copy to your GP.