Thyroid conditions during pregnancy

What is the thyroid?

The thyroid is a tiny, butterfly-shaped gland in the front of your neck. The thyroid makes hormones (chemicals) that play a big role in your health. For example, thyroid hormones can affect your heart rate and your metabolism (how your body uses energy).

Sometimes the thyroid gland makes too much or too little of these hormones. When this happens, you have a thyroid disorder. Some people have a thyroid disorder that begins before pregnancy (also called a preexisting condition). Others may develop thyroid problems for the first time during pregnancy or after pregnancy.

With treatment, most thyroid conditions can be managed, which reduces the risk of complications for both you and your baby. If untreated, thyroid conditions can cause problems for you and your baby during pregnancy and after birth.

What are the most common kinds of thyroid conditions?

There are two main kinds of thyroid conditions:

1. Hyperthyroidism (“hyper” means too much). This happens when the thyroid is overactive and makes too much thyroid hormone. This condition can cause many of your body’s functions to speed up. Hyperthyroidism during pregnancy usually is caused by an autoimmune disorder called Graves’ disease. If you have Graves’ disease, your immune system makes antibodies that cause your thyroid to make too much thyroid hormone.
2. Hypothyroidism (“hypo” means too little or not enough). This happens when the thyroid is underactive and makes too little thyroid hormones, so many of your body’s functions slow down. Hypothyroidism during pregnancy usually is caused by an autoimmune disorder called Hashimoto’s disease. When you have Hashimoto’s disease, your immune system makes antibodies that attack your thyroid and damage it so it can’t produce thyroid hormones.

Both conditions can cause complications during pregnancy, but proper treatment helps lower risks.

How are thyroid conditions during pregnancy diagnosed?

Health care providers don’t usually test your thyroid before or during pregnancy unless you:

• Have symptoms of a thyroid condition
• Have a history of thyroid disease
• Are at higher risk due to conditions like diabetes or autoimmune disorders

A blood test can check your thyroid hormone levels and thyroid stimulating hormone (also called TSH) in your body. TSH is a hormone that tells your thyroid gland to make thyroid hormones. If you think you may have a thyroid condition, ask your provider about testing.

Are you at risk for having a thyroid condition during pregnancy?

You may be at higher risk for thyroid conditions during pregnancy if you:

• Are already being treated for a thyroid condition.
• Have had a thyroid condition in the past (including after giving birth).
• Have an autoimmune disorder or you have a family history of autoimmune thyroid disease, like Graves’ disease or Hashimoto’s disease. 
• Have type 1 diabetes. 
• Have had high-dose neck radiation or treatment for hyperthyroidism. 

If you have any of these risk factors, or think you may be at risk, talk to your provider about whether thyroid testing is right for you.

What are signs and symptoms of a thyroid disorder?

Signs of hyperthyroidism (overactive thyroid) include:

• Fine or brittle hair that breaks easily.
• Goiter.
• Graves’ ophthalmology. This condition can cause your eyeballs to bulge out and your eyelids to pull back. It can cause your eyes to be red and painful and can cause vision problems.
• Losing weight (which may happen quickly) or not gaining enough weight during pregnancy.
• Shaking hands and fingers.
• Thinning skin.

Symptoms of hyperthyroidism include:

• Being more sensitive to heat or unusual sweating.
• Changes in your moods, like being nervous or anxious (worried), being irritable (easily annoyed and angered) or having mood swings.
• Changes in your menstrual period before pregnancy.
• Fast heartbeat (tachycardia), irregular heartbeat (arrhythmia), or pounding heart (heart palpitations).
• Having bowel movements more often.
• Muscle weakness.
• Trouble sleeping or fatigue (being very tired and having little energy).

How can hyperthyroidism affect pregnancy?

Hyperthyroidism that’s untreated or not treated correctly is linked to:

• Preeclampsia. This is a serious blood pressure condition that can happen after the 20th week of pregnancy or after giving birth (also called postpartum preeclampsia). 
• Pulmonary hypertension. This is a kind of high blood pressure that happens in the arteries in your lungs and on the right side of your heart.
• Placental abruption. This is a serious condition in which the placenta separates from the wall of the uterus before birth. 
• Heart failure. This is when your heart can’t pump enough blood to the rest of your body.
• Thyroid storm. This is when your symptoms suddenly get much worse. It’s a rare, but life-threatening condition during pregnancy. Pregnant women who have thyroid storm are at high risk of heart failure.

Problems for babies can include:

• Preterm birth. 
• Goiter.
• Low birthweight.
• Miscarriage or stillbirth. 

What are signs and symptoms of hypothyroidism?

Signs of hypothyroidism (underactive thyroid) include:

• Dry skin or dry, thinning hair.
• Goiter.
• High cholesterol. 
• Hoarse or husky voice.
• Slow heart rate.
• Sweating less.
• Weight gain and puffy face.

Symptoms of hypothyroidism include:

• Being more sensitive to cold.
• Constipation. 
• Depression. 
• Fatigue (being really tired).
• Muscle and joint pain or stiffness, weak muscles, or muscle cramps.
• Problems with memory or problems being able to focus or pay attention.
• Problems with menstrual periods or with fertility (being able to get pregnant).

How can hypothyroidism affect pregnancy?

Untreated hypothyroidism during pregnancy is linked to:  

• Anemia. This is when you don’t have enough healthy red blood cells to carry oxygen to the rest of your body.
• Gestational hypertension. This is high blood pressure that starts after 20 weeks of pregnancy and goes away after you give birth.
• Preeclampsia.
• Placental abruption.
• Postpartum hemorrhage (also called PPH). This is when a woman has heavy bleeding after giving birth.
• Myxedema, a rare condition caused by severe, untreated hypothyroidism.
• Heart failure. 

Problems for babies can include:

• Infantile myxedema, a condition that’s linked to severe hypothyroidism that can cause dwarfism, intellectual disabilities, and other problems.
• Low birthweight.
• Problems with growth and brain and nervous system development.
• Thyroid problems. This is rare, but it can happen in babies of women with Hashimoto’s disease because the antibodies can cross the placenta during pregnancy.
• Miscarriage or stillbirth.

What is postpartum thyroiditis?

Some people develop this condition, which is an autoimmune condition that can happens within the first year after birth. It can cause your thyroid to be overactive, underactive and even a combination of both.

If you feel extremely tired, experience mood changes, or have other unusual symptoms after giving birth, talk to your provider about thyroid testing.

How are thyroid conditions treated during pregnancy and while breastfeeding?

Most medicines used to treat thyroid conditions during pregnancy are safe for your baby. Thyroid medicines can help keep the right level of thyroid hormones in your body. Your provider gives you blood tests during pregnancy to check your TSH and T4 levels to make sure your medicine is at the right amount (also called dose). T4 is a hormone made by your thyroid.

If you’re already taking thyroid medicine when you get pregnant, keep taking it and talk to your provider about it as soon as possible. Your provider may want to adjust or change your medicine to make sure it’s safe for your baby.

Treating hyperthyroidism. If you have mild hyperthyroidism, your healthcare provider may monitor your condition without starting treatment. For more severe cases, there are different treatments that can help manage your thyroid hormone levels.

Certain medicines may have risks or side effects depending on when they are taken. Because of this, it’s important to talk to your provider about the safest options for you and your baby. As an example, radioactive iodine is a type of treatment for hyperthyroidism this is generally not recommended during pregnancy, as it may affect the baby’s thyroid.

If you’re breastfeeding, some thyroid medicines may be used at low doses, but you should speak with your provider to understand the benefits and any potential risks.

Since every pregnancy is different, talking about your treatment options, risks, and benefits with your healthcare provider is the best way to ensure the right care for you and your baby.

Treating hypothyroidism. If you have hypothyroidism, your healthcare provider may recommend treatment to help manage your thyroid hormone levels during pregnancy. Some medications may be used to replace thyroid hormones that your body isn’t making enough.

If you were already taking medicine for hypothyroidism before pregnancy, your provider may need to adjust your dose to make sure your thyroid levels stay within a healthy range. Regular blood tests during pregnancy can help monitor these levels.

If you are breastfeeding, speak with your provider to understand what medicine is best to treat hypothyroidism.

More information

• American Thyroid Association
• MotherToBaby

Last reviewed: February 2025

See also: Prescription medicine during pregnancy