Managing Thyroid Disease During and After Pregnancy

Thyroid disease is known to affect many aspects of pregnancy and postpartum health, as well as the health of your baby. In an effort to organize the various and sometimes contradictory practices with regarding thyroid disease and pregnancy, clinical guidelines for the management of thyroid problems in pregnancy and during the postpartum period were published in late 2011, and as of 2016, were considered current recommendations.

The journal Thyroid published the guidelines as a 47-page article, titled "Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and Postpartum". This article includes some of the key recommendations of the guidelines, which have important implications if you develop thyroid disease during or after your pregnancy, or you who have a diagnosed thyroid condition prior to becoming pregnant.


Thyroid Screening in Pregnancy

Pregnant woman at doctor
PeopleImages / Getty Images

In general, universal thyroid screening in pregnant women is not considered justifiable according to the Guidelines. The experts do suggest, however, that screening and evaluation be conducted among women who face a higher risk of thyroid disease.

You are a higher risk for thyroid disease during pregnancy if you: 

  • have a personal history of thyroid dysfunction and/or thyroid surgery
  • have a family history of thyroid disease
  • have a goiter
  • test positive for elevated thyroid antibodies
  • have symptoms or clinical signs that may suggest hypothyroidism
  • have type I diabetes
  • have a history of either miscarriage or preterm delivery
  • have other autoimmune disorders that are often linked to autoimmune thyroid problems, such as: vitiligo, adrenal insufficiency, hypoparathyroidism, atrophic gastritis, pernicious anemia, systemic sclerosis, systemic lupus erythematosus and Sjogren's syndrome
  • have experienced infertility
  • have previously received radiation to the head or neck area as a cancer treatment, or have had multiple dental x-rays
  • are morbidly obese, which is defined as a body mass index (BMI) of over 40, or a body weight that is 20% or more over ideal body weight
  • are age 30 or older
  • have been treated with amiodarone (Cordarone) for heart rhythm irregularities
  • have been treated with lithium
  • have been exposed to iodine in a medical test contrast agent in the previous six week


Pregnant woman taking pills
Anna Bizon / Getty Images

Hypothyroidism while you are pregnant can have significant adverse health effects on the unborn baby, and so maternal hypothyroidism should be avoided.

If you are hypothyroid prior to pregnancy, the Guidelines recommend that your dosage be adjusted so that TSH is below 2.5 mIU/L prior to conception. This lowers the risk of the TSH elevating in the first trimester.

You should also confirm your pregnancy as early as possible, and have a plan in place to increase your medication dosage immediately, in order to protect your pregnancy by supporting your thyroid function.

If you are diagnosed as hypothyroid during pregnancy, you should be treated without delay, with the goal of restoring your thyroid levels to normal as quickly as possible. During the first trimester, the TSH level should be maintained at a level of between 0.1 and 2.5 mIU/L, 0.2 to 3.0 mIU/L during the second trimester, and 0.3 to 3.0 mIU/L in the third trimester.

By the time you are four to six weeks pregnant, your dose of thyroid medication will usually need to be increased, potentially by as much as 50 percent.

If you have autoimmune thyroid disease, for example, you've previously tested positive for thyroid antibodies, you are at risk of becoming hypothyroid at any point in the pregnancy. You should be monitored regularly through the pregnancy for elevated TSH.

You will also want to be aware of changes to expect to your thyroid during pregnancy.

Another important recommendation: make sure that your prenatal vitamin includes iodine, an essential nutrient for thyroid function during pregnancy.



pregnant woman at doctor
BSIP / Getty Images

If you have lower-than-normal TSH levels, you should be evaluated to determine if the cause of the hyperthyroidism during pregnancy is transient hyperthyroidism/hyperemesis gravidarum—a condition of pregnancy that causes severe morning sickness—or Graves' disease. The diagnosis is made by determining if you have a goiter, and/or test positive for thyroid antibodies.

If you are pregnant, and become hyperthyroid due to Graves’ disease or nodules, you should begin hyperthyroidism treatment right away. Typically, you would receive antithyroid drug treatment (if newly diagnosed), or, if you are already being treated, your dosage will be adjusted so that your free T4 levels remain in the normal range for someone who is not pregnant.

The antithyroid drug of choice (especially during the first trimester) is propylthiouracil because methimazole has a slightly higher (though very small) risk of causing birth defects in your baby. The Guidelines recommend switching to methimazole for the second and third trimesters.

If you have a severe negative reaction to antithyroid drugs, require very high doses to control your hyperthyroidism, or have uncontrolled hyperthyroidism despite treatment, surgery may be recommended. The surgery would usually be recommended during your second trimester when it is least likely to endanger your pregnancy.

An important note: Radioactive iodine treatment should never be given if you are or might be pregnant.


Thyroid Antibodies, Graves', and your Newborn

Doctor checking a newborn (real people)
Juanmonino / Getty Images

If you have TSH receptor-stimulating or TSH receptor-binding antibodies, they can cross the placenta and affect your baby’s thyroid. If you are positive for these antibodies during pregnancy, your baby can be born with hyperthyroidism or hypothyroidism. These antibodies should, therefore, be measured if you have Graves’ disease, or if you have previously had newborns who developed Graves’ disease. It may also be necessary to treat you with antithyroid drugs during pregnancy in order to reduce risk to your baby. 

If you have elevated TSH receptor-stimulating or TSH receptor-binding antibodies and are treated with antithyroid drugs, fetal ultrasound evaluation should be conducted. This ultrasound should look for evidence of thyroid dysfunction in your developing baby, including slow growth and enlarged thyroid, among other signs.

If you are a new mother with Graves’ disease, your newborn should be evaluated for thyroid dysfunction after birth, as there is a risk of a condition known as neonatal hyperthyroidism: which has serious implications for newborns.


Morning Sickness and Hyperthyroidism

Pregnant Woman Sitting on Bathroom Floor with Box of Tissues between Knees
Glasshouse Images / Getty Images

All pregnant women with hyperemesis gravidarum (severe morning sickness that includes substantial weight loss and dehydration) should have thyroid function evaluated.

If you have severe morning sickness, and overt hyperthyroidism due to Graves’ disease, and gestational hyperthyroidism with significantly elevated thyroid hormone levels—free T4 above the reference range and TSH less than 0.1 µU/ml—you may require short-term treatment with an antithyroid drug.


Thyroid Nodules and Thyroid Cancer

thyroid ultrasound, active surveillance, thyroid cancer, papillary thyroid cancer

According to the Guidelines, if you are pregnant and have thyroid nodules, you should have TSH and Free T4 measured. If you have a family history of medullary thyroid carcinoma or multiple endocrine neoplasia (MEN) 2, calcitonin levels should also be measured.

The Guidelines also recommend ultrasound to determine the features of the nodule and monitor growth. If a nodule is less than 10mm in size, a fine-needle aspiration (FNA) biopsy of your thyroid is not required unless there are suspicious characteristics.

If a nodule is growing, or you have a persistent cough or vocal problems, or any other suspicious indicators from the history, the Guidelines recommend an FNA be performed. FNA is considered safe during pregnancy.

When cancerous thyroid nodules are discovered during the first or second trimester, surgery should be offered in your second trimester. Well-differentiated thyroid cancers grow slowly, so if the evaluation indicates that the cancer is papillary or follicular, and there is no evidence of advanced disease, you may be offered the opportunity to wait until after your baby is born before having surgery.

If you are currently and are diagnosed with thyroid cancer, in some cases your doctor will recommend waiting until after delivery for surgery. But you can receive treatment with thyroid hormone replacement drugs, to keep your TSH low, but still detectable. Ideally, your free T4 or total T4 levels should remain within the normal range for pregnancy.

Radioactive iodine should not be given if you are currently pregnant or breastfeeding. 

After you receive a therapeutic dose of radioactive iodine, you should wait six months to a year to become pregnant, to ensure that your thyroid function is stable and that your thyroid cancer is in remission.


Postpartum Thyroid Problems

Mother playing with baby girl outdoors
Sam Diephuis / Getty Images

If you have a history of postpartum thyroiditis, you are at a substantially increased risk of developing hypothyroidism. You should have an annual thyroid evaluation.

Typically, antithyroid drugs are not recommended for the hyperthyroid period of postpartum thyroiditis. If you have postpartum thyroiditis and are symptomatic, a beta blocker may be used. The recommended beta blocker is propranolol, at the lowest possible dose to relieve symptoms.

The Guidelines recommend that after your hyperthyroid phase, your TSH should be monitored every two months until 1 year postpartum, to screen for hypothyroidism.

If your symptoms are severe, or if you are planning to conceive, hypothyroidism triggered by postpartum thyroiditis should be treated. If you are asymptomatic, the Guidelines recommend having your TSH rechecked every four to eight weeks.

If hyperthyroidism appears after your pregnancy, the Guidelines recommend that your hyperthyroidism be treated, but recommends that if needed, the first choice of medication be the antithyroid drug known as methimazole (brand name Tapazole). Doses up to 20 to 30 mg/d are considered safe for a nursing mother and her baby. The second choice for antithyroid medication after pregnancy is propylthiouracil (known as PTU), at doses up to 300mg/d. Experts have more concerns regarding use of PTU due to problems with liver toxicity that are associated with the drug.

If you are nursing and taking antithyroid drugs, the Guidelines recommend that the dosages of antithyroid medication be divided, and taken at times of day that occur after breastfeeding. If you are taking antithyroid drugs and breastfeeding, your baby should also be screened periodically with thyroid function tests, according to the Guidelines.


Breastfeeding With Thyroid Disease

Mother breastfeeding baby girl (0-1 month)
Andria Patino / Getty Images

Many new mothers choose to breastfeed. If you have a thyroid condition, you may wonder about the safety of breastfeeding.

If you are being treated for hypothyroidism while breastfeeding, you can safely continue to take thyroid hormone replacement medication at your appropriate dosage without harm to your baby. 

The question of taking antithyroid drugs for hyperthyroidism while breastfeeding is a bit more controversial, and you may want to explore the pros and cons further. 

You also should be aware of the guidelines and some specific recommendations regarding how you can safely have a thyroid scan while breastfeeding

Was this page helpful?
Article Sources
  • Stagnaro-Green, Alex, et. al. "Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and Postpartum." Thyroid. Volume 21, Number 10, 2011.