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Hypothyroidism in Pregnancy - Causes, Symptoms, Diagnosis, and Treatment

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Hypothyroidism is an endocrine disorder marked by an underactive thyroid gland and is a common finding during pregnancy. Read this article to know more.

Medically reviewed by

Dr. Sameer Kumar

Published At December 2, 2022
Reviewed AtJanuary 29, 2024

What Is Hypothyroidism in Pregnancy?

Hypothyroidism is an endocrine disorder characterized by an underactive thyroid gland and may be present during pregnancy. Many symptoms of hypothyroidism resemble those of pregnancy, such as fatigue, dry skin, constipation, and weight gain. In addition, low thyroid hormone levels can interfere with getting pregnant or cause miscarriage and premature delivery.

What Is a Thyroid Gland and What Is Its Function?

The thyroid gland is a tiny, butterfly-shaped gland present in the neck of females. The thyroid makes thyroid hormones that can affect heart rate and metabolism. However, the thyroid gland sometimes makes too much or too little of certain hormones; it is called a thyroid disorder. A woman can develop thyroid disorder before pregnancy (pre-existing condition), during pregnancy, or after baby delivery.

The two main types of thyroid conditions are as follows-

  1. Hyperthyroidism- When the thyroid gland is overactive and makes excess thyroid hormone. This condition speeds up many body functions. It is caused by an autoimmune disorder called Graves' disease during pregnancy. Hyperthyroidism in pregnancy can cause hyperemesis gravidarum (excessive nausea and vomiting during pregnancy).

  2. Hypothyroidism- When the thyroid gland is underactive and does not make enough thyroid hormones causing body functions to slow down. Hypothyroidism during pregnancy is caused by an autoimmune disorder called Hashimoto's disease.

What Are the Symptoms of Hypothyroidism in Pregnancy?

Hypothyroidism is a widespread medical condition and can go undetected in mild cases due to a lack of symptoms. In hypothyroidism, the thyroid gland becomes less active and produces insufficient hormones. The most common symptoms of hypothyroidism in pregnancy are as follows-

  • Feeling tired.

  • Cold intolerance.

  • Swelling of the face.

  • Weight gain.

  • Constipation.

  • Hoarse voice.

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

  • Carpal tunnel syndrome (tingling sensation or pain in hands).

  • Muscular cramps.

  • Trouble concentrating.

  • Irregular menstrual periods.

  • Slow heart rate.

What Are the Causes of Hypothyroidism in Pregnancy?

Hypothyroidism in pregnancy is usually caused by an autoimmune disorder called Hashimoto's disease. In this disease, the immune system makes antibodies that attack the thyroid, causing inflammation and decreasing the production of thyroid hormones.

How Is Hypothyroidism Diagnosed in Pregnancy?

Few women are at a higher risk of developing hypothyroidism during pregnancy. These risk factors include-

  • Family or personal history of thyroid disease.

  • Maternal age more than 30.

  • Type 1 diabetes.

  • Radiation exposure of head and neck.

  • Multiple miscarriages.

  • Infertility issues.

  • Morbid obesity.

  • Iodine-deficient region.

Some blood tests are performed to measure thyroid hormone levels based on the symptoms. For example, thyroid antibody tests can be done to check if Hashimoto's disease is the reason for hypothyroidism.

What Is a Thyroid Function Test?

A thyroid function test (TFT) is a blood test that measures thyroid hormone (thyroxine, or T4) and serum TSH (thyroid-stimulating hormone) levels to check for hypothyroidism. Hypothyroidism is often present when TSH levels are above average, and T4 levels are below normal.

Since both low and high thyroid hormone levels can harm the developing fetus, treatment aims to keep the levels within the normal range. Thyroid-stimulating hormone (TSH) elevation in pregnancy is usually indicative of hypothyroidism.

The pituitary gland secretes a hormone called TSH, which causes the thyroid to produce thyroid hormones (T4 and T3). A fetus that is developing during pregnancy may be affected by an elevated TSH level, which indicates that the thyroid hormones are low.

Expectant mothers with hypothyroidism must collaborate closely with their medical professionals to periodically assess thyroid function and alter medication dosages as necessary.

What Is the Treatment of Hypothyroidism in Pregnancy?

  • Pregnant women with hypothyroidism and no significant or mild symptoms do not need active treatment, but they require monitoring and regular checkups throughout their pregnancy.

  • Treatment for hypothyroidism involves replacing the hormone that the thyroid gland cannot produce.

  • Levothyroxine is the primarily prescribed medication for hypothyroidism in pregnancy. It is a thyroid hormone medicine similar to T4 ( thyroxine hormone produced by the thyroid gland). Levothyroxine is safe for the baby and vital until it can make its thyroid hormone. Hypothyroidism prescription can be acquired through teleconsultation.

  • The increment of the Levothyroxine dose is based on the degree of TSH (thyroid-stimulating hormone) levels elevation.

  • Serum TSH levels should be measured every four to six weeks until 20 weeks of gestation or when the patient is on a stable medication dose.

  • Antenatal testing is not required in women with well-controlled hypothyroidism, but it is recommended for patients with coexisting maternal or obstetric indications.

  • Levothyroxine doses should be decreased to the pre-pregnancy dosage levels post-delivery over four to six weeks.

  • Hypothyroidism is a lifelong progressive disease, and the doses of thyroid hormone replacement may need adjustment from time to time. So, regular checkups and monitoring are recommended.

What are the Mother's Risks of Having Hypothyroidism?

Improperly treated or neglected hypothyroidism has been linked to

  • Pre-eclampsia.

  • Congestive heart failure.

  • Maternal anemia.

  • Placental anomalies.

  • Postpartum hemorrhage (bleeding).

  • Increased risk of miscarriage.

Women who have severe hypothyroidism are more likely to experience these complications. Additionally, there seems to be an increased risk in women who have antibodies against thyroid peroxidase (TPO). Women who have mild hypothyroidism may not experience any symptoms at all or might attribute their symptoms to being pregnant.

What are Baby's Risks Associated with Maternal Hypothyroidism?

Thyroid hormones play an important role in the growth and development of the brain during the first trimester which in turn leads to cognitive and intellectual development. Maternal Hypothyroidism can pose risks to the baby such as

  • Developmental Issues.

  • Low birth weight.

  • Impaired Cognition.

As soon as pregnancy is confirmed, a TSH test should be taken to rule out thyroid issues. It is important to monitor the thyroid levels throughout pregnancy.

What Is Postpartum Thyroiditis?

Postpartum thyroiditis is also an autoimmune disorder like Hashimoto's disease. It occurs when a woman's thyroid gland gets inflamed after baby delivery. Postpartum thyroiditis can first make the thyroid overactive (hyperthyroidism), but over time the condition leads to an underactive thyroid (hypothyroidism). The treatment is based on the severity and type of symptoms.

Can a Woman With Hypothyroidism Have a Healthy Pregnancy?

A woman with hypothyroidism can have a healthy pregnancy with minimal maternal and fetal risk by taking the medications prescribed by doctors in recommended doses and having regular thyroid function tests each trimester. Early diagnosis and quick treatment are keys to achieving favorable outcomes.


Pregnancy is a period of great physiological stress on both the mother and the fetus. However, if pregnancy is compounded by hypothyroidism, maternal and fetal outcomes can be adverse. Hypothyroidism is common in pregnant women but is often a missed diagnosis. However, timely detection and prompt treatment of the disorder can result in good fetal and maternal outcomes.

Frequently Asked Questions


Will Hypothyroidism During Pregnancy Affect the Fetus?

Yes, hypothyroidism during pregnancy can affect the fetus. If people do not get treated, it leads to premature birth, low birth weight, and development delay. Therefore, pregnant women must have their thyroid levels checked and the necessary treatment to ensure the fetus's health.


What Are the Most Common Causes of Hypothyroidism in Pregnancy?

In pregnancy, hypothyroidism is the most common reason for developing an autoimmune disorder called Hashimoto's thyroiditis. Such a condition occurs when the immune system attacks the thyroid gland. That leads to inflammation and the decreased function of the thyroid.


Can Hypothyroidism Be Considered a High-Risk Pregnancy?

Hypothyroidism can interfere with the fertilized egg. This can increase the risk of miscarriage. In addition, if one is pregnant and hypothyroidism is not treated, one's baby may be born prematurely before the predicted date, and weight that is less than normal and lower mental capacity.


Can One Have a Healthy Pregnancy With Hypothyroidism?

Hypo is meant for underactive thyroid function. Therefore, one can have a healthy pregnancy and protect their baby's health by having regular thyroid function tests and taking medicine the doctor prescribes.


How Can One Fix Hypothyroidism When Pregnant?

Levothyroxine is one of the most commonly used thyroid medications during pregnancy. This levothyroxine replaces the T4 that the thyroid is unable to produce. It is safe to take this medication during pregnancy.


Can One Deliver a Child When the Mother Has Hypothyroidism?

Children delivered by mothers with hypothyroidism during pregnancy have a lower IQ and impaired psychomotor, both motor and mental development.


What Is Considered Normal Levels of the Thyroid During Pregnancies?

Thyroid during pregnancy ranges from 0.1 - 2.5 mlU/L during the first trimester, 0.2 - 3.0 mlU/L during the second trimester, and 0.3 - 3.5 mlU/L during the third trimester.


What Happens if a Pregnant Mother's Hypothyroidism Is Left Treated?

In cases of untreated hypothyroidism that has an increased risk of miscarriage and has associated with the following such as,
 - Maternal anemia.
 - Postpartum hemorrhage.
 - Placental abnormalities.
 - Pre-eclampsia.


How Can One Control TSH Levels Through Food?

One can control the TSH by intaking the following:
 - Cabbage. 
 - Cauliflower.
 - Kale.
 - Bok choy.
 - Turnips. 
 - Because digesting these vegetables can block the thyroid's ability to utilize the iodine essential for normal thyroid function.


Which Fruit Is Good for the Thyroid?

Fruits that are good for the thyroid are pears, plums, and citrus fruits, which have abundant pectin that helps detoxify the body of mercury and is one of the most critical metals connected to thyroid problems.
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Dr. Sameer Kumar
Dr. Sameer Kumar

Obstetrics and Gynecology


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