Problems with your thyroid can occur throughout pregnancy, leaving both mother and baby potentially at risk serious of complications if not addressed. The best way to avoid this is to ensure that thyroid problems are well treated and managed. The first step towards this is to have your thyroid function checked by your doctor.

All expectant mothers are advised to have the health of their thyroid checked at least once in the early stages of pregnancy.

It is particularly important to have your thyroid checked if you suffer endometriosis or polycystic ovary syndrome, as you are more likely to also have problems with your thyroid.1

Iodine deficiency

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. Even a mild iodine shortage during pregnancy can have negative effects on the delivery and development of your baby; including their thyroid becoming underactive. It is therefore recommended that all pregnant and breast feeding women should take a nutritional supplement containing iodine every day.2

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 breast-feeding.3

An underactive thyroid and pregnancy

Approximately 5% of women develop an underactive thyroid (hypothyroidism) during pregnancy.4 However, it can often go unnoticed as the symptoms can be similar to the changes in your body which occur naturally during pregnancy, such as putting on weight, feeling tired and swelling.

If left untreated, hypothyroidism in pregnancy can be potentially very dangerous. It can increase the risk of premature birth, as well as leaving the baby at risk of learning and development problems. Hypothyroidism can also cause the placenta to loosen from the inner wall of the uterus before the baby is born, this is a serious condition called placental abruption. In some cases, placental abruption can be life-threatening for both mother and baby.5,6

Treatment for hypothyroidism is the same regardless of whether a woman is pregnant or not. Taken orally, levothyroxine is a drug used to replace missing thyroid hormones and is recommended throughout pregnancy and while breast feeding.7 Treatment for hypothyroidism during pregnancy is extremely important as it protects both mother and baby from any potential future complications. Women with hypothyroidism prior to pregnancy will require a higher levothyroxine dosage before becoming pregnant and more frequent check-ups or monitoring during pregnancy to make sure their dose of levothyroxine is correct.

An overactive thyroid and pregnancy

An overactive thyroid (hyperthyroidism) in pregnant women is rare and in most cases is caused by Graves’ disease.8 Graves’ disease is an autoimmune disease which causes the thyroid gland to over produce hormones, resulting in hyperthyroidism.

Failure to treat hyperthyroidism during pregnancy can increase the risk of still birth and premature birth, as well as increase the risk of child deformities and pre-eclampsia.8

Treatment for pregnant women with hyperthyroidism is sometimes different to those offered to other women, as some of the medications available can harm the unborn baby.

  • Women with mild hyperthyroidism and not experiencing symptoms are closely monitored during their pregnancy, however, there is no call for treatment if both mother and baby are doing well.
  • Women with severe hyperthyroidism experiencing symptoms will be treated with an anti-thyroid medication such as methimazole or propylthioracil (PTU). PTU is usually the preferred treatment option during the first trimester of pregnancy.8
  • In some cases, pregnant women will have surgery to partially remove their thyroid gland if they are allergic to a medication or if they require such high doses that it could damage the baby.8

Did you know?

Iodine can commonly be found in sea fish, seafood, bread, cheese, cow’s milk, eggs, yoghurt and seaweed2.


  • 1Poppe K, Velkeniers B, Glinoert D: Thyroid disease and female reproduction. Clinical Endocrinology, 2007: 66(3): 309-321
  • 2American Thyroid Association. Iodine Deficiency Accessed March 2009
  • 3Management of Thyroid Dysfunction during Pregnancy and Postpartum: An Endocrine Society Clinical Practice Guideline. 2007
  • 4Fast Facts For Your Health. Thyroid Disease and Women. National Women’s Health Resource Center. Red Bank, NJ.2006
  • 5ACOG Education Pamphlet AP128-Thyroid Disease. American College of Obstetricians and Gynecologists. Washington, DC. 2002
  • 6Mayo Clinic. Accessed March 2009
  • 7Poppe K, Velkeniers B, Glinoer D; Medscape. The role of thyroid autoimmunity in fertility and pregnancy. Nat Clin Pract Endocrinol Metab. 2008;4:394-405
  • 8American Thyroid Association. Thyroid Disease and Pregnancy. Accessed March 2009
  • 9Bettendorf M. Thyroid disorders in children from birth to adolescence. Eur J Nucl Med Mo Imaging. 2002;29 Suppl 2:S439-46
  • 10Brown R et al. Congenital Hypothyroidism. The Hormone Foundation. 2009
  • 11Thyroid Disease in Children. Accessed March 2009
  • 12Lee PA. The effects of manipulation of puberty on growth. Horm Res. 2003;60:60-7