Hypothyroidism During Pregnancy: Causes, Symptoms And Treatment

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Hypothyroidism in pregnancy is a condition caused by an underactive thyroid gland, which secretes insufficient thyroid hormones, thyroxine (T4), and triiodothyronine (T3). These hormones play a key role in assisting normal fetal brain development during pregnancy (1).

The underactive thyroid gland can therefore affect the growth and development of the fetus since the fetus depends on the thyroid hormones for up to 18 to 20 weeks of pregnancy. In addition, hypothyroidism could cause complications because the signs usually go unnoticed (2) (3).

Read on the post to know the causes, risk factors, symptoms, complications, and treatment of hypothyroidism during pregnancy.

Causes And Risk Factors For Hypothyroidism During Pregnancy

The following are some causes and risk factors for maternal hypothyroidism (4):

  • Hashimoto disease: This autoimmune disease causes the immune system to produce thyroid peroxidase (TPO) antibodies that attack the thyroid gland. This results in an underproduction of thyroid hormones.
  • Iodine deficiency: Since iodine is required for thyroid hormone production, its deficiency can lead to decreased synthesis.
  • History of thyroid problems: The treatment for hyperthyroidism (excessive production of thyroid hormones) aims at reducing the hormone levels, which may lead to hypothyroidism. Additionally, a history of thyroid disease may also increase the risk of hypothyroidism during pregnancy.
  • Other treatments: Surgeries or radiation therapies to remove thyroid tumors or other treatments around the neck could cause hypothyroidism.
  • Postpartum thyroiditis: Some pregnant women may experience Postpartum thyroiditis (inflammation of the thyroid gland) after delivery. This condition may start with hyperthyroidism and progress to hypothyroidism.
  • Age: Pregnant women over 30 years may be at an increased risk.
  • History of medical conditions: A history of infertility, preterm delivery, or type-1-diabetes may increase the risk.

Symptoms And Signs Of Hypothyroidism In Pregnancy

The common symptoms of hypothyroidism may include the following (5) (6):

  • Hoarse voice
  • Fatigue
  • Shortness of breath
  • Irregular menstruation
  • Slow heart rate
  • Constipation
  • Cold intolerance
  • Swollen face
  • Hair and skin changes (dry skin and loss of eyebrows)
  • Brittle nails
  • Muscle cramps
  • Carpal tunnel syndrome (tingling in hands and legs)

Since a few of these symptoms mimic the signs of pregnancy, hypothyroidism symptoms may go unnoticed in pregnancy.

Diagnosis Of Hypothyroidism During Pregnancy

To check your thyroid levels, your medical provider may conduct a blood test and physical exam. The thyroid function tests check your T3, T4, and thyroid-stimulating hormone (TSH) levels. TSH is a hormone secreted by the pituitary gland that intimates the thyroid gland to produce thyroid hormones.

A high TSH level and low T4 level indicate hypothyroidism. The TSH levels are high since the lack of T4 stimulates the pituitary to produce more TSH to raise the T4 levels. Alternatively, a high TSH and a normal T4 may indicate borderline hypothyroidism.

Also, if hypothyroidism is diagnosed, your health care provider may recommend a TPO antibody determination test to check for Hashimoto disease (4).

Treatment Of Hypothyroidism During Pregnancy

Replacement of thyroid hormones with levothyroxine is the primary treatment for hypothyroidism during pregnancy. However, it is only available on prescription. This medication should not be taken with prenatal pills containing iron and calcium as they may hinder levothyroxine absorption. A gap of at least four hours should be maintained between both pills (7).

If you are diagnosed with hypothyroidism before pregnancy, consult your healthcare provider before conception since they may normalize the hormone levels.

After pregnancy, your usual dosage may be increased by 20–30% to meet the fetal demand. In addition, routine screening of your thyroid profile is required to ensure the thyroid hormone dosage is sufficient. Usually, the levels are checked every four weeks for the first half of the pregnancy (8).

After delivery, the pre-pregnancy dosage may be used for a woman with pre-established hypothyroidism. Simultaneously, the newborn may be tested for congenital hypothyroidism.

Complications Of Hypothyroidism In Pregnancy

Hypothyroidism in pregnancy can affect the mother and fetus if unidentified on time and cause the following complications depending on the severity:

For the mother

Hypothyroidism in pregnant women increases the risks of (7) (8)

  • Congestive heart failure (inefficient pumping)
  • Placental abnormalities
  • Myopathy (muscle pain and weakness)
  • Myxedema (severe hypothyroidism leading to coma or death)

For the baby/fetus

Hypothyroidism during pregnancy may have long-lasting effects on the baby, such as impaired brain development, hindering neurological and cognitive development. The risk is higher if the pregnancy is undetected in the first trimester. Hypothyroidism could also cause the following fetal complications (5) (7):

  • Preterm birth
  • Thyroid problems
  • Low birth weight
  • Goiter (swelling of the neck due to enlarged thyroid gland)
  • Infantile myxedema (leading to dwarfism and intellectual disabilities)

Since thyroid illnesses pose severe maternal and fetal consequences, getting tested for hypothyroidism during pregnancy is essential.

Frequently Asked Questions

  1. Can I have a healthy pregnancy with hypothyroidism?

Yes, you can have a healthy pregnancy with hypothyroidism, provided it is timely diagnosed and appropriately treated. Ensure that you receive hormonal treatment before, during, and after the pregnancy (2) (7).

  1. Can hypothyroidism cause a high-risk pregnancy?

Due to the adverse effects of hypothyroidism on the mother and baby, a pregnancy with hypothyroidism can be considered a high-risk one. Hence, the thyroid hormone levels must be carefully monitored and balanced before, during, and after pregnancy (4).

Unidentified and untreated hypothyroidism during pregnancy has risks. Hence, get your thyroid levels tested before conception. Normalizing the hormonal levels before pregnancy could be crucial for maternal and fetal health for those with a history of thyroid issues.


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Sindusha MS

Sindusha is a clinical nutritionist with over two years of experience in diverse fields of nutrition. She did her Masters in Food Science and Nutrition and has qualified UGC-NET. She interned as a quality control analyst and as a dietitian during her graduation. She was a part of several community nutrition projects and a phytochemical-based nutrition study during the same... more