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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:

The Thyroid Gland
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Hypothyroidism in pregnancy can also be caused by:

  • Hashimoto disease, the most common cause
  • Not enough treatment for pre-existing hypothyroidism
  • Over treating hyperthyroidism


Graves disease is overactivity of the thyroid. It is the most common cause. Very high levels of human chorionic gonadotropin (hCG) is another cause. This may get better on its own.

Risk Factors

You may be at risk of this problem if you have:

  • A personal or family history of a thyroid problem
  • Been treated for a thyroid problem
  • A goiter
  • Hyperemesis gravidarum , a severe form of morning sickness
  • A personal or family history of immune problems


Symptoms of hypothyroidism are:

Symptoms of hyperthyroidism are:

  • Losing weight without trying
  • Fast or abnormal heart rhythm
  • Sweating
  • Nervousness
  • Shaking
  • Bulging eyes
  • Diarrhea
  • Problems sleeping


Your doctor will ask about your symptoms and health history. A physical exam will be done.

Your doctor will test your thryoid hormone levels. Other blood tests may also be done. Pictures of your thyroid may need to be taken. You may need to see a doctor who treats hormone problems.



Medicine can replace the hormone.


Mild hyperthyroidism will be watched closely. Some women may need to take medicine. Pregnancy hormones can cause changes in thyroid hormone levels. 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 is no way to prevent thyroid problems in pregnancy.


The American Congress of Obstetricians and Gynecologists  http://www.acog.org 

American Thyroid Association  http://www.thyroid.org 


The Society of Obstetricians and Gynaecologists of Canada  https://sogc.org 

Thyroid Foundation of Canada  http://www.thyroid.ca 


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 Plus website. Available at:  https://www.dynamed.com/topics/dmp~AN~T115280/Graves-disease-in-adults . Updated September 24, 2018. Accessed March 25, 2019.

Hashimoto’s disease. Family Doctor—American Academy of Family Physicians website. Available at: https://familydoctor.org/condition/hashimotos-disease/. Updated September 27, 2017. Accessed March 25, 2019.

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. Updated December 2017. Accessed March 25, 2019.

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

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