Skip to main content


URMC / Encyclopedia / Content

Hypothyroidism and Pregnancy

Picture of an expectant mother holding her belly

Facts about hypothyroidism and pregnancy

Hypothyroidism is a condition marked by an underactive thyroid gland and may be present during pregnancy. Many symptoms of hypothyroidism are similar to pregnancy symptoms. For example, fatigue, weight gain, and abnormal menstruation are common to both. Having low thyroid hormone levels may even interfere with becoming pregnant or be a cause of miscarriage. 

What are the symptoms of hypothyroidism?

Hypothyroidism is a common condition. It can go undetected if symptoms are mild. Hypothyroidism means the thyroid is underactive and making insufficient amounts of thyroid hormones. Symptoms of hypothyroidism may be mild and may start slowly. The following are the most common symptoms of hypothyroidism:

  • Feeling tired

  • Unable to stand cold temperatures

  • Hoarse voice

  • Swelling of the face

  • Weight gain

  • Constipation

  • Skin and hair changes, including dry skin and loss of eyebrows

  • Carpal tunnel syndrome (hand tingling or pain)

  • Slow heart rate

  • Muscle cramps

  • Trouble concentrating

  • Irregular menstrual periods

The symptoms of hypothyroidism may resemble other conditions or medical problems. Always talk with your healthcare provider for a diagnosis.

How does hypothyroidism affect the fetus?

During the first few months of pregnancy, the fetus relies on the mother for thyroid hormones. Thyroid hormones are important in normal brain development and growth of the fetus. Hypothyroidism in the mother can have long-lasting effects on the fetus. 

How is thyroid function tested?

You will have blood test that measures thyroid hormone (thyroxine, or T4) and serum TSH (thyroid-stimulating hormone) levels to check for hypothyroidism. Hypothyroidism is often suspected when TSH levels are above normal and T4 levels are below normal.

Who should undergo thyroid function screening?

Routine screening for hypothyroidism during pregnancy is not recommended. A pregnant woman with symptoms of hypothyroidism, a history of hypothyroidism, or with other endocrine system conditions should be screened.

How is hypothyroidism treated during pregnancy?

Thyroid hormone replacement is used to treat the mother. Dosage of thyroid hormone replacement therapy is based on the individual's levels of thyroid hormones. Thyroid hormone levels may change during pregnancy. And, the thyroid replacement dosing may also change. Thyroid hormone levels need to be checked every 4 weeks during the first half of pregnancy. The treatment is safe and essential to both mother and fetus. Routine screening for all newborns includes a test of thyroid hormone levels.

Medical Reviewers:

  • Holloway, Beth Greenblatt, RN, M.Ed.
  • Hurd, Robert, MD