Your Health

The thyroid gland is a small organ, but it has a big impact.



Pregnancy causes a number of normal physiological and hormonal changes that impact the thyroid gland and may lead to increased thyroid hormone requirements.1 The baby is also dependent on the mother for its supply of thyroid hormones during pregnancy, especially in the first trimester if the fetal thyroid is not yet active.1 It is paramount that your thyroid gland is functioning properly during this critical period, and expectant mothers are advised to have the health of their thyroid checked as soon as pregnancy is detected.

Note: It is particularly important to have your thyroid checked if you suffer from endometriosis or polycystic ovary syndrome (PCOS), as you are more likely to have problems with your thyroid if you have these conditions.2

Underactive thyroid and pregnancy

If left untreated, hypothyroidism in pregnancy can be very dangerous. Thyroid hormone is critical for brain development and can leave the baby at risk for learning and development problems.1


Treatment for hypothyroidism is the same regardless of whether a woman is pregnant or not. Taken orally, appropriate medication is recommended throughout pregnancy.1 Treatment for hypothyroidism during pregnancy is extremely important as it protects both the mother and baby from any potential future complications. Women with hypothyroidism prior to pregnancy will require a higher dose of the appropriate medication before becoming pregnant and more-frequent monitoring during pregnancy to make sure their medication dose is correct.1

Iodine deficiency and pregnancy

Iodine is vital for the production of thyroid hormones, and as your body does not produce iodine, it must be consumed as part of a healthy diet.3 Even a mild iodine shortage during pregnancy can have negative effects on the delivery and development of your baby, including your baby’s thyroid becoming underactive.1 It is therefore recommended that all pregnant and breastfeeding women take a nutritional supplement containing iodine every day.3 Women of childbearing age should have an average iodine intake of 150 micrograms per day, which should be increased to approximately 250 micrograms during pregnancy and to approximately 290 micrograms while breastfeeding.3

Overactive thyroid and pregnancy

An overactive thyroid (hyperthyroidism) in pregnant women is caused, in most cases, by Graves’ disease.1 Graves’ disease is an autoimmune disease that causes the thyroid gland to overproduce hormones, resulting in hyperthyroidism.

Failure to treat hyperthyroidism during pregnancy can increase the risk for stillbirth, premature birth and child deformities.1

The treatment for pregnant women with hyperthyroidism is sometimes different to that offered to other women, as some of the medications available can harm the unborn baby.1

  • Women with mild hyperthyroidism who are not experiencing symptoms will be closely monitored during their pregnancy; however, there is no call for treatment if both mother and baby are doing well.1
  • Women with severe hyperthyroidism who are experiencing symptoms will be treated with an anti-thyroid medication such as methimazole or propylthiouracil. The latter is usually the preferred treatment option during the first trimester of pregnancy.1
  • Beta-blockers can be used to help treat heart palpitations and tremor associated with hyperthyroidism but should be used sparingly during pregnancy and only until hyperthyroidism is controlled with anti-thyroid medication.2
  • In some cases, a pregnant woman will have surgery to partially remove the thyroid gland if she is allergic to a medication or if she requires high doses that could harm the baby.1
  1. Poppe K, Velkeniers B, Glinoer D. Thyroid disease and female reproduction. Clin Endocrinol (Oxf) 2007: 66: 309–321.
  2. American Thyroid Association. Thyroid disease and pregnancy. Available at Last accessed February 2022
  3. American Thyroid Association. American Thyroid Association (ATA) on the potential risks of excess iodine ingestion and exposure. Available at Last accessed February 2022


Date of preparation: February 2022