Thyroid and Pregnancy
Thyroid and Pregnancy

Thyroid health is very important when it comes
to pregnancy,

Regardless of whether you’re already pregnant or trying to conceive.

Hypothyroidism in Pregnancy

Having Trouble Conceiving?1

The problem may be your thyroid gland.

Reproductive health can be affected by hypothyroidism. In fact, some experts recommend that women having trouble getting pregnant have their TSH levels checked. If you have high TSH, you could have hypothyroidism.

Before turning to costly procedures like IVF, make sure your doctor conducts a TSH blood test to check your TSH levels. The good news is that with proper levothyroxine therapy, hypothyroidism may not have a major impact on fertility.

Already Pregnant?

It’s important to watch for thyroid disease when you’re expecting because pregnancy causes major changes in thyroid function.2

An untreated, underactive thyroid gland (hypothyroidism) may increase the risk of having a miscarriage or stillbirth.2 Uncontrolled hypothyroidism, especially in the first trimester, may affect a baby's growth and brain development.2

Ask your doctor about getting a TSH blood test to see if your TSH levels are too high, as this is a sign of thyroid disease. If you do have hypothyroidism, getting treatment can help you and your baby.

Hypothyroidism & Planning to Get Pregnant

If you suffer from hypothyroidism, are currently being treated with levothyroxine, and are planning a pregnancy, there are some important things that you should know.

Talk to your doctor about your pregnancy plans, as your medication dose may need to increase before you become pregnant.3

You should have a TSH blood test every 4 to 6 weeks during the first half of your pregnancy and a TSH blood test at least once after 30 weeks of your pregnancy.3

Contact your doctor right away after a missed period (menstrual cycle) or positive home pregnancy test, as your dose of levothyroxine will likely need to be increased.3

After delivery, your dose of levothyroxine is usually reduced to what you were taking before your pregnancy.1

Experts strongly recommend that hypothyroidism should not be treated with desiccated thyroid during pregnancy.4

A TSH blood test should usually be performed at about 4 to 6 weeks after giving birth.5

Thyroid & Pregnancy Facts

Pregnancy causes major changes in thyroid function.

0.3% - 0.5%

0.3% to 0.5% of pregnant women have overt hypothyroidism.*5
*overt hypothyroidism is characterized by increased TSH levels but reduced
values of thyroid hormones.6

5%

Postpartum thyroiditis is seen in about 5% of
women.7

15% - 28%

In iodine-sufficient regions, about 15% to 28% of pregnant
women have subclinical hypothyroidism.7

Both overt and subclinical hypothyroidism may have negative effects on pregnancy and fetal development, such as:

  • Increased incidence of miscarriage and preterm delivery5
  • Potential damage to the development of the baby’s brain7

Which Women Should Have A TSH Blood Test During Their Pregnancy?

A TSH blood test will reveal if your TSH levels are high. High TSH levels can be indicative of hypothyroidism.2

Certain women should have a TSH blood test early in their pregnancy to detect thyroid disease.8

They include women with:

  • Age above 30 years5
  • A history of autoimmune disease5 or prior thyroid surgery9
  • A family history of thyroid disease5
  • A goitre (an enlarged thyroid)9
  • Thyroid antibodies7
  • Hyperemesis gravidarum and clinical features suggestive of hyperthyroidism5
  • Type I diabetes9
  • Previous radiation therapy to the head or neck9
  • A history of miscarriage or preterm delivery7
  • Decreased fertility9
  • A BMI greater than or equal to 40 (being very overweight)7
  • A need for amiodarone (a drug for irregular heartbeats), lithium,7 or recent administration of iodinated contrast agent (often used during a CT scan)10
  • Living in an area of known moderate to severe iodine insufficiency5

Abbreviations: BMI, Body Mass Index; CT, Computed Tomography; TSH, Thyroid Stimulating Hormone

References:

1. Pregnancy and fertility in thyroid disorders. British Thyroid Foundation. Accessed May 17, 2023. https://www.btf-thyroid.org/pregnancy-and-fertility-in-thyroid-disorders 2. Pregnancy and thyroid disease. National Institutes of Health. Accessed May 17, 2023. https://www.niddk.nih.gov/-/media/Files/Endocrine-Diseases/Pregnancy_Thyroid_ Disease_508.pdf 3. Thyroid disease & pregnancy. National Institute of Diabetes and Digestive and Kidney Diseases. Accessed May 17, 2023. https://www.niddk.nih.gov/health-information/endocrine-diseases/pregnancy-thyroid-disease 4. Hypothyroidism in pregnancy. American Thyroid Association. Accessed May 18, 2023. https://www.thyroid.org/wp-content/uploads/patients/brochures/hypothyroidism_pregnancy_faq.pdf 5. Smith A, Eccles-Smith J, D’Emden M, Lust K. Thyroid disorders in pregnancy and postpartum. Aust Prescr. 2017;40(6):214-219. 6. Bekkering GE, Agoritsas T, Lytvyn L, et al. Thyroid hormones treatment for subclinical hypothyroidism: a clinical practice guideline. BMJ. 2019;365:I2006. 7. Deshauer S, Wyne A. Subclinical hypothyroidism in pregnancy. CMAJ. 2017;189(28):E941. 8. Hypothyroidism and pregnancy. John Hopkins Medicine. Accessed August 7, 2023. https://www.hopkinsmedicine.org/health/conditions-and-diseases/staying-healthy-during-pregnancy/hypothyroidism-and-pregnancy 9. Sahay RK, Nagesh VS. Hypothyroidism in pregnancy. Indian J Endocrinol Metab. 2012;16(3):364-370. 10. Lee SY, Rhee CM, Leung AM, Braverman LE, Brent GA, Pearce EN. A review: radiographic iodinated contrast media-induced thyroid dysfunction. J Clin Endocrinol Metab. 2015;100(2):376-383.