It is difficult to advise a woman about the safety of medications in pregnancy since there might be long-term drug effects of which we are unaware. Each woman has to weigh the benefits versus the risks.
Hypothyroidism and Pregnancy
Signs of an underactive thyroid gland (hypothyroidism) may be masked by pregnancy. But the thyroid is important for your baby's brain development. Learn if you should be screened for hypothyroidism.
Featured Treatment Areas
Maternal-Fetal Medicine Program
The Maternal-Fetal Medicine Program at Massachusetts General Hospital provides obstetric sub-specialty care to families with complicated or high-risk pregnancies.
The Obstetrics Program at Massachusetts General Hospital provides state-of-the-art, individualized care for women before, during and after childbirth.
Hypothyroidism and Pregnancy
Facts about hypothyroidism and pregnancy
Hypothyroidism is a condition that is caused by an underactive thyroid gland. It may happen during pregnancy. Many symptoms of the condition are similar to pregnancy symptoms. For example, they can both cause fatigue, weight gain, and changes in menstruation. Having low thyroid hormone levels can also cause problems with becoming pregnant. It can also be a cause of miscarriage.
What are the symptoms of hypothyroidism?
Hypothyroidism is a common condition. It can go undetected if symptoms are mild. The thyroid doesn't make enough thyroid hormones. Symptoms may be mild and may start slowly. The most common symptoms include:
Inability to stand cold temperatures
Swelling of the face
Skin and hair changes, including dry skin and loss of eyebrows
Carpal tunnel syndrome (hand tingling or pain)
Slow heart rate
Shortness of breath with activity
Muscle cramps, weakness, joint pain
Irregular menstrual periods
The symptoms may be like other health problems. Talk with your healthcare provider for a diagnosis.
How does hypothyroidism affect the baby in the womb?
During the first few months of pregnancy, the baby relies on the mother for thyroid hormones. These hormones are vital for normal brain development and growth of the baby. Hypothyroidism in the mother can have long-lasting effects on the baby.
How is thyroid function tested?
You will have blood tests that measure thyroid hormone (thyroxine, or T4) and serum TSH (thyroid-stimulating hormone) levels. TSH levels that are above normal and T4 levels that are below normal may mean you have hypothyroidism.
Who should have thyroid function testing?
Routine screening for hypothyroidism during pregnancy is not advised. A pregnant woman with symptoms of hypothyroidism, a history of the condition, or with other endocrine system conditions should be tested.
How is hypothyroidism treated during pregnancy?
Thyroid hormone replacement is used to treat the mother. The amount of thyroid hormone given is based on the mother's levels of thyroid hormones as well as her symptoms. Thyroid hormone levels may change during pregnancy. The hormone replacement dose will likely change over time. Thyroid hormone levels need to be checked every 4 weeks in the first half of pregnancy. The levels may be checked less often during the second half of pregnancy as long as the dose does not change. The treatment is safe and vital to both mother and baby. Thyroid hormones should not be taken at the same time as prenatal vitamins. This is because the minerals in the vitamins may stop the absorption of the thyroid hormone. All newborns are screened at birth to check thyroid hormone levels.
News & Publications
The Patient Gateway provides secure online access to your health information whenever you need it. Check upcoming appointments, communicate with your doctor’s office, review medications and pay medical bills—all seamlessly online 24/7.