Hypothyroidism and Pregnancy: What you should know

Hypothyroidism and Pregnancy: What you should know

Young woman or girl shows positive pregnancy test with two stripes. Lifestyle background. Pregnancy family concept.
Dr. Natalie Bessom
Medically reviewed by

Natalie Bessom, D.O. Board-certified family medicine doctor with specialty training in nutrition, USA

Hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormone, is a common concern during pregnancy. It can pose various risks for both the mother and the fetus, making understanding and managing this condition essential for a healthy pregnancy.

Despite nearly 45% of all pregnancies in the U.S. being unintended, an increasing number of women are choosing to plan their pregnancies. In medical terms, this planning phase is known as preconception care. For women intending to conceive, it is crucial to recognize the significance of maintaining optimal thyroid function, as it plays a vital role in ensuring the health and well-being of both mother and baby.

In order to cope with the physical changes and demands during pregnancy, the thyroid often goes through a number of noticeable changes. However, an undiagnosed thyroid problem may put mothers at risk of having issues when trying to conceive and during pregnancy. These problems can include miscarriages, infertility, and menstruation issues. 

This article examines, the following questions will be answered: 

What are the common causes and symptoms of hypothyroidism in pregnancy?

Pregnant Woman

Iodine is an essential nutrient vital and necessary nutrient for the production of thyroid hormones and for human development. Globally, iodine deficiency is the leading cause of hypothyroidism.

However, in iodine-sufficient populations such as in the United States, the most common cause of hypothyroidism is Hashimoto’s thyroiditis. Hashimoto’s thyroiditis is an autoimmune disease where the body attacks its own healthy thyroid cells. 

Common symptoms of hypothyroidism include: 

  • Thinning of hair
  • Weight gain
  • Bloating
  • Heartburn 
  • Constipation 
  • Brain Fog 
  • Dry or rough skin
  • Aches and pains of muscles 

What are the risks of hypothyroidism to the mother and baby?

African young man in mask measuring the pulse of pregnant woman and caring about her health at hospital

Throughout pregnancy, the thyroid hormone is critical for the brain development and overall growth of the baby. Mothers who have been diagnosed with hypothyroidism should have their thyroid health and levels checked as soon as the pregnancy is confirmed. 

Hypothyroidism affects between 3-5% of all pregnant women and, it left untreated,  can lead to complications such as: 

  • preeclampsia
  • low birth weight
  • premature birth
  • impaired brain development of the child
  • respiratory problems in the newborn

Some studies have also found a strong association between severe iodine deficiency during pregnancy and an increased risk of:

Who needs to be tested for hypothyroidism?

Hypothyroidism during pregnancy often goes undiagnosed, primarily due to the overlap of its symptoms—like fatigue and weight gain—with common pregnancy experiences, making them easy to dismiss. Additionally, not all regions or medical institutions practice universal screening for thyroid dysfunction in pregnant women; instead, many only screen those at high risk, such as individuals with a history of thyroid issues. This approach can miss cases among those without evident risk factors. The variability in thyroid levels during pregnancy and the lack of consistent application of pregnancy-specific thyroid function test norms further complicate the diagnosis.

According to the 2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum, routine thyroid laboratory tests are not recommended for all women planning a pregnancy. However, all women who opt for a preconception consultation or attend their first pregnancy appointment should undergo a clinical evaluation. If any of the following risk factors are identified, testing for serum levels of thyroid-stimulating hormone (TSH) is recommended:

  • History of hypothyroidism or hyperthyroidism
  • Current symptoms or signs of thyroid dysfunction
  • High levels of anti-thyroid antibodies
  • The presence of a goiter
  • History of radiation to the head or neck or prior thyroid surgery
  • Age (above 30 years)
  • Type 1 diabetes or other autoimmune disorders
  • History of pregnancy loss, preterm delivery, or infertility
  • Multiple prior pregnancies (2 or more)
  • Family history of autoimmune thyroid disease or thyroid dysfunction
  • Morbid obesity (Body Mass Index of or greater than 40 kg/m2)
  • Use of amiodarone or lithium, or recent administration of iodinated radiologic contrast
  • Residing in an area of moderate to severe iodine deficiency

According to these guidelines, when low serum TSH levels are detected in the first trimester, it is recommended to review the medical history, perform a physical examination, and test the levels of FT4 or TT4 in the serum. Additionally, assessing TRAb and TT3 levels may be useful in determining the cause of thyrotoxicosis.

How is hypothyroidism during pregnancy treated?

The main goal for treating hypothyroidism during pregnancy is to ensure that there is an adequate replacement of thyroid hormones for the health of mother and child. 

The most common treatment for hypothyroidism is synthetic thyroid hormone, levothyroxine (LT4)

Because thyroid hormone levels change during pregnancy, a hypothyroid woman’s medication dosage should also be adjusted once pregnancy is confirmed. An increase in levothyroxine dosage by 25% to 50% is usually recommended.

Additionally, regular monitoring of thyroid function helps ensure that thyroid hormone levels are within the normal range during the pregnancy. According to the American Thyroid Association, thyroid function tests should be performed every 4 weeks during the first half of pregnancy. 

The American Thyroid Association also recommends that levothyroxine should not be taken at the same time as prenatal vitamins and should be separated by at least 4 hours. This is because prenatal vitamins contain iron and calcium and can interfere with the absorption of the medication. 

Most importantly, pregnant women should always consult and follow the advice of their healthcare provider in order to minimize risks and complications.


What is postpartum thyroiditis?

Postpartum thyroiditis is an inflammatory condition of the thyroid gland that typically occurs within the first year after childbirth. It affects about 5-10% of women and can manifest as transient hyperthyroidism followed by hypothyroidism. While the hyperthyroid phase often goes unnoticed, the hypothyroid phase can cause symptoms like fatigue and depression. Most women eventually recover normal thyroid function, but some may develop permanent hypothyroidism.

Women are at greater risk of developing postpartum thyroiditis if they have: 

  • An autoimmune disorder 
  • High levels of antithyroid antibodies 
  • A history of thyroid dysfunction
  • A history of postpartum thyroiditis 
  • A  family history of thyroid dysfunction or diseases

Mothers who are aware of these conditions or experience symptoms postpartum should consult their healthcare provider immediately.

Key Takeaways

  • Hypothyroidism affects 3-5% of pregnant women and requires careful monitoring and management to prevent complications such as preeclampsia and developmental issues in children.
  • Symptoms of hypothyroidism can overlap with normal pregnancy symptoms, often leading to undiagnosed cases.
  • Universal screening for thyroid dysfunction during pregnancy is not consistently practiced, which may contribute to undiagnosed cases of hypothyroidism.
  • Maintaining optimal thyroid function is crucial during the preconception phase to promote a healthy pregnancy and fetal development.
  • Postpartum thyroiditis occurs in about 5-10% of women, initially presenting as hyperthyroidism followed by hypothyroidism, and can lead to permanent thyroid dysfunction in some cases.
  • High levels of thyroid antibodies increase the risk of developing conditions like postpartum thyroiditis.


Hypothyroidism during pregnancy can lead to various complications, including an increased risk of miscarriage, preterm birth, and developmental issues for the baby. It’s crucial for pregnant individuals with hypothyroidism to manage their condition effectively to minimize these risks.

Pregnant individuals with hypothyroidism should focus on consuming foods rich in nutrients vital for thyroid health, such as iodine, selenium, vitamin D, and zinc. Incorporating foods like eggs, nuts, yogurt, and salmon can help support thyroid function during pregnancy.

It’s essential for pregnant individuals with hypothyroidism to continue taking their prescribed thyroid medications as directed by their healthcare provider. Maintaining thyroid hormone levels within the appropriate range is crucial for both maternal and fetal health throughout pregnancy.

Pregnant individuals with hypothyroidism can optimize their pregnancy outcomes by closely monitoring their thyroid function through regular medical check-ups and following their healthcare provider’s recommendations for medication dosage adjustments as needed. Additionally, maintaining a balanced diet rich in thyroid-supportive nutrients and managing stress levels can contribute to a healthy pregnancy despite hypothyroidism.


At ThyForLife, we do our utmost to provide accurate information. For detailed medical information regarding diagnosis, treatment, and general practices please consult your healthcare professional. Always listen to the advice of your healthcare provider.
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