Featuring Sonal Chaudhry, MDReviewed by Alexandra Schwarz, MD | September 17, 2024

Key takeaways:

Hypothyroidism can make it difficult to get pregnant. Starting treatment with thyroid medication can improve your chances of becoming pregnant.
A blood test can detect hypothyroidism by measuring the levels of thyroid stimulating hormone (TSH). TSH levels should be 2.5 mIU/L or less during pregnancy.
With treatment, it’s possible to have a safe pregnancy and delivery when you have hypothyroidism.

Featuring Sonal Chaudhry, MDReviewed by Alexandra Schwarz, MD | September 17, 2024

If you’re pregnant or planning to be, the last thing you might be thinking about is your thyroid. But it’s very important — not having enough thyroid hormone can affect your chances of getting pregnant.

During pregnancy, untreated hypothyroidism can cause problems for both you and your baby. But know that it’s simple to test for and treat an underactive thyroid (hypothyroidism) during pregnancy.

What is hypothyroidism?

Hypothyroidism — or an underactive thyroid — occurs when the thyroid doesn’t make enough hormones to meet the body’s demands.

The thyroid is a butterfly-shaped gland located in the front of your neck. It makes the thyroid hormones T3 and T4 that affect your metabolism — or how your body stores and uses energy.

A chemical from the brain known as thyroid stimulating hormone (TSH) regulates thyroid hormone production. When thyroid hormone levels are low, the brain sends out TSH to tell the thyroid to make more.

A blood test can check for hypothyroidism by measuring TSH levels. If your TSH is high, that means your thyroid hormone levels are likely low.

Can hypothyroidism affect my chances of getting pregnant?

The short answer is yes.

Hypothyroidism can cause irregular periods, which makes ovulation harder to track. Some people with hypothyroidism don’t ovulate at all.

In a study of women with infertility, 24% had hypothyroidism. After starting medication for their hypothyroidism, almost 80% of those women got pregnant within 6 weeks to 1 year. According to the American College of Obstetrics and Gynecology (ACOG), women who are experiencing difficulties getting pregnant should have their thyroid levels checked.

How does hypothyroidism affect a growing baby?

If left untreated, hypothyroidism can affect a developing baby. Studies have shown that babies are more likely to be born early (prematurely) if exposed to low thyroid hormone levels during pregnancy. They’re also more likely to have:

Low weight at birth
Breathing problems
Delays in development
Lower IQ

But during pregnancy, a low thyroid level can lead to maternal complications that can affect a baby’s health like:

Bleeding and placental abruption (hemorrhage)
Anemia (not enough blood cells)
High blood pressure during pregnancy and pre-eclampsia

What can cause hypothyroidism to appear during pregnancy?

During pregnancy, the body uses more thyroid hormone to keep up with the needs of a growing baby. So pregnancy itself actually makes signs of hypothyroidism more likely.

If you have a history of hypothyroidism and have been receiving treatment before getting pregnant, your medication dose may not be able to keep up with your increased needs. This will make it seem like your hypothyroidism is worse. But studies show many people need a dose that’s 25% to 50% higher once they become pregnant.

If you have a history of hypothyroidism and become pregnant, your healthcare provider will check your hormone levels throughout your pregnancy and make adjustments to your thyroid medication.

Risk factors for hypothyroidism include:

A family history of thyroid disease: You have a higher chance of developing hypothyroidism if one of your close relatives has it. This includes parents, grandparents, or siblings.
An enlarged thyroid: An enlarged thyroid (often called a goiter) can occur when the gland is working in overdrive. Eventually, it might not be able to keep up, which can lead to inadequate thyroid hormone production and hypothyroidism.
An autoimmune disease: Autoimmune diseases like rheumatoid arthritis, celiac disease, and Type 1 diabetes are conditions in which the body’s immune system attacks its own cells. If you have one, your chances of getting autoimmune thyroid disease, Hashimoto’s thyroiditis, is higher, and this could lead to hypothyroidism.
Radiation to the area: The same radiation beams that kill the cancer cells can also damage the body’s normal tissues. So, radiation to treat head and neck cancers can hurt the thyroid gland as a side effect.
Iodine deficiency: The thyroid gland uses iodine to make thyroid hormone, so not getting enough iodine can lead to low thyroid hormone levels. Iodine deficiency is less of an issue in the United States because iodine is added to salt and other foods to prevent iodine deficiency. But if you’re avoiding foods and salt that contain iodine, you may be at risk for iodine deficiency, especially if you’re pregnant.

What are common signs of hypothyroidism during pregnancy?

This is the tricky part. The symptoms of hypothyroidism are similar to what you might feel in a normal pregnancy. They include:

Tiredness
Low mood
Weight gain
Feeling cold
Dry skin and hair
Constipation

Many of these symptoms overlap with common symptoms during pregnancy.

The ACOG guidelines say healthcare providers should not routinely test for hypothyroidism. Testing is only recommended in cases where people have risk factors for developing hypothyroidism during pregnancy. The test is also recommended if you develop symptoms of hypothyroidism during pregnancy.

So keep your healthcare provider updated on how you’re feeling and give them a full rundown of your medical history, including medications you take, how your previous pregnancies turned out, and if you have any family members with hypothyroidism. This will help your provider decide whether to order blood tests to check for hypothyroidism.

How is hypothyroidism treated during pregnancy?

Levothyroxine is a medication that treats hypothyroidism. It’s a lab-made version of human thyroid hormone and will bring your TSH and thyroid hormones levels back to normal.

According to the FDA, levothyroxine is safe to take in pregnancy.

Levothyroxine is available in different forms and brands, including:

Your healthcare provider will check your TSH levels throughout your pregnancy to make sure they’re within normal limits. Too little thyroid hormone can be harmful to you and your baby but so is too much thyroid hormone (hyperthyroidism).

Your provider will adjust your medication so your TSH levels remain within normal range during your pregnancy. Your TSH level should be 2.5 mIU/L or less during your pregnancy.

Can you have a successful pregnancy with hypothyroidism?

Yes!

If you have hypothyroidism, you’ll need your thyroid levels checked during pregnancy. And you’ll need treatment, too. But you can still have a successful pregnancy and a healthy baby.

Just remember to always take your medication and stay up to date with your medical appointments. Don’t change your medication dosage unless your provider tells you to do so. You can also see an endocrine specialist (endocrinologist) if you receive a diagnosis of hypothyroidism during your pregnancy.

The bottom line

Hypothyroidism — or underactive thyroid — can develop during pregnancy. You’re more likely to have hypothyroidism if you have a family history of hypothyroidism or a condition that affects your thyroid.

Symptoms of hypothyroidism overlap with pregnancy symptoms and include constipation, low mood, and fatigue. If you’re at risk for hypothyroidism or have symptoms, let your healthcare provider know. They can check your blood for signs of hypothyroidism and start treatment if needed. With treatment, you can have a safe pregnancy and a healthy baby.

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Written by:

Maryann Mikhail, MD

Maryann Mikhail, MD, is a board-certified dermatologist and medical writer based in South Florida. She is the founder of Waverly DermSpa in Fort Lauderdale and holds a voluntary faculty position at the Dr. Phillip Frost Department of Dermatology and Cutaneous Surgery at the University of Miami MIller School of Medicine.

Edited by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

Reviewed by:

Adriena Beatty D.O., MBA, CPE

Adriena Beatty, DO, MBA, CPE, is an Army veteran and board-certified obstetrician and gynecologist with over 20 years of experience. She is a graduate from Tuskegee University with a degree in chemical engineering and chemistry.

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