The thyroid is a butterfly-shaped gland in the front of the neck. Pregnancy hormones can cause changes to thyroid hormone levels. This can raise the risk of pregnancy problems when it is not treated. There are two types of problems:
- Hypothyroidism —the thyroid gland does not make enough thyroid hormone
- Hyperthyroidism —the thyroid gland makes too much thyroid hormone
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Hypothyroidism in pregnancy may be caused by:
- An immune system problem known as Hashimoto disease, the most common cause
- Not enough treatment for pre-existing hypothyroidism
- Over treating hyperthyroidism
Hyperthyroidism in pregnancy may be caused by:
- Overactivity of the thyroid gland known as Graves disease, the most common cause
- Very high levels of human chorionic gonadotropin (hCG)
Things that may raise the risk of this problem are:
Hypothyroidism problems are:
Hyperthyroidism problems are:
The doctor will ask about your symptoms and health history. A physical exam will be done.
Your thyroid hormone levels will be tested. Other blood tests may also be done.
Images may be taken of the thyroid.
Medicine will be given to replace the hormone. Thyroid levels will be checked often and the dose may need to be changed.
Mild hyperthyroidism will be watched closely. Some people may need to take medicine. Your medicine needs may change during pregnancy. Your doctor will check your thyroid hormone levels every 6 to 8 weeks during pregnancy and 4 weeks after a change in dose.
If medicine does not work, the thyroid gland may need to be removed. Radioiodine is used to destroy the thyroid gland. It is rarely done during pregnancy because of the risk to the fetus.
There are no known methods to prevent this health problem. Proper prenatal care can help to find problems before they happen.
The American Congress of Obstetricians and Gynecologists
American Thyroid Association
The Society of Obstetricians and Gynaecologists of Canada
Thyroid Foundation of Canada
American College of Obstetricians and Gynecologists. Practice Bulletin No. 148: Thyroid disease in pregnancy. Obstet Gynecol. 2015;125(4):996-1005.
Graves disease in adults. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/graves-disease-in-adults. Accessed August 24, 2021.
Hashimoto’s disease. Family Doctor—American Academy of Family Physicians website. Available at: https://familydoctor.org/condition/hashimotos-disease. Accessed August 24, 2021.
Pregnancy & thyroid disease. National Institute of Diabetes and Digestive and Kidney Diseases website. Available at: https://www.niddk.nih.gov/health-information/endocrine-diseases/pregnancy-thyroid-disease. Accessed August 24, 2021.
Smith TJ, Hegedüs L. Graves' Disease. N Engl J Med. 2016 Oct 20;375(16):1552-1565, commentaries can be found in N Engl J Med 2017 Jan 12;376(2):184, N Engl J Med 2017 Jan 12;376(2):185.
Last reviewed July 2021 by EBSCO Medical Review BoardBeverly Siegal, MD, FACOG Last Updated: 8/24/2021