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Pregnancy and Thyroid Disease - Symptoms, Diagnosis, and Treatment

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Thyroid diseases during pregnancy can cause severe complications like premature birth, miscarriages, and other disorders. Read to know more.

Written by

Dr. Asna Fatma

Medically reviewed by

Dr. Richa Agarwal

Published At May 15, 2023
Reviewed AtJuly 6, 2023


Thyroid disorders are the second most prevalent endocrine disorder affecting young women in their reproductive or fertile age. If left untreated, these thyroid diseases can cause multiple complications during pregnancy, like growth retardation, premature birth, low birth weight of the baby, elevated risks of miscarriages, increased blood pressure of the mother, etc. Therefore, it is very important to screen women with thyroid problems, women with a family history of hyper or hypothyroidism, autoimmune disorders, diabetes, and so on. The three most common thyroid diseases affecting pregnant women are hyperthyroidism (overactive thyroid), hypothyroidism (underactive thyroid), and postpartum thyroiditis (inflammation of the thyroid gland after childbirth).

What Is the Thyroid Gland and What Are Thyroid Diseases?

The thyroid gland is an endocrine gland responsible for producing the thyroid hormones thyroxine (T4), triiodothyronine (T3), and calcitonin. The thyroid is a small gland shaped like a butterfly, which is highly vascular and located in the front of the neck. The thyroid glands consist of two lobes and an isthmus (a band of tissues connecting the two lobes). Several conditions can lead to dysfunction of the thyroid gland, which in turn causes an imbalance in the thyroid hormone levels. Thyroid hormones are crucial for growth, development, and regulating metabolism in the body. This imbalance in the level of thyroid hormones leads to multiple thyroid diseases. Some of the most common thyroid diseases are hyperthyroidism (overactive thyroid), hypothyroidism (underactive thyroid), goiter (lump in the thyroid gland), thyroiditis (inflammation of the thyroid gland), etc.

What Are the Roles of Thyroid Hormones in Pregnancy?

The thyroid hormones play a vital role in pregnancy. Some of these roles are:

  • Thyroid hormones are significant for the development and growth of the fetus, along with the development of the baby's brain and nervous system.

  • During the first three months of the pregnancy, the baby is dependent on the mother's thyroid hormone, which comes from the placenta, to grow. After the twelfth week, the baby's thyroid gland starts producing hormones, but the amount of thyroid hormone produced is not sufficient for growth and development. By the twentieth week of pregnancy, the baby's thyroid starts producing an adequate amount of thyroid hormones.

  • During pregnancy, the mother's thyroid gland also slightly enlarges in size, and the thyroid hormone levels are also elevated.

What Are the Common Thyroid Diseases That Occur in Pregnancy?

Some of the common thyroid diseases that occur during pregnancy are hypothyroidism, hyperthyroidism, and postpartum thyroiditis (which occurs after childbirth).

  1. Hyperthyroidism: An overactive thyroid gland produces excessive thyroid hormones leading to a condition known as hyperthyroidism. The most common cause of hyperthyroidism during pregnancy is Graves' disease, which is an autoimmune disease. On average, one to four in every 1000 pregnant women suffer from Graves' disease during pregnancy in the United States. In Graves' disease, the mother's immune system starts producing antibodies (thyroid-stimulating immunoglobins) which in turn stimulates the thyroid gland to produce more thyroid hormones. In rare cases, high levels of human chorionic gonadotropin during early pregnancy can cause hyperthyroidism, which usually subsides after a few months.

  2. Hypothyroidism: An underactive thyroid gland produces an inadequate amount of thyroid hormones leading to a condition known as hypothyroidism. The most common cause of hypothyroidism during pregnancy is Hashimoto's disease, which is an autoimmune disorder. In Hashimoto's disease, the mother's immune system produces anti-thyroid antibodies, which start attacking the thyroid cells leading to reduced production of thyroid hormones.

What Are the Symptoms of Hyperthyroidism During Pregnancy?

Some of the symptoms of hyperthyroidism are similar to the symptoms seen during early pregnancy like

  • Fatigue.

  • Tiredness.

  • Heat intolerance.

  • Rapid heartbeat.

  • Other symptoms of hyperthyroidism during pregnancy include irregular heartbeat, trembling of hands, and unusual weight loss.

What Are the Symptoms of Hypothyroidism During Pregnancy?

The symptoms of hypothyroidism during pregnancy are usually very mild, and they may go unnoticed for a long time. However, the common symptoms of hypothyroidism during pregnancy are:

  • Extreme tiredness or fatigue.

  • Cold intolerance.

  • Constipation.

  • Muscular cramps.

  • Absent-mindedness.

How Does Hyperthyroidism Affect Pregnancy?

An untreated hyperthyroidism during pregnancy can cause multiple complications and health conditions for the mother as well as the baby. Hyperthyroidism during pregnancy can lead to the following problems in the mother:

  • Miscarriage: Miscarriage is the condition in which the baby dies in the womb of the expecting mother before 20 weeks of pregnancy.

  • Stillborn Baby: In this pregnancy complication, the baby dies in the womb after 20 weeks of pregnancy.

  • Preeclampsia: It is a condition characterized by dangerously high blood pressure after 20 weeks of pregnancy or after childbirth. The mother will also show symptoms of improper functioning of the liver and kidneys. Along with elevated blood pressure, proteinuria (increased level of protein in the urine) is also a significant finding to confirm preeclampsia.

  • Pulmonary Hypertension: Elevated blood pressure in the pulmonary arteries and the arteries present on the right side of the heart.

  • Placental Abruption: In this pregnancy complication, the placenta separates from the wall of the uterus before birth.

  • Thyroid Storm: It is a potentially life-threatening condition in which the symptoms of hyperthyroidism worsen, and it can lead to heart failure in the mother.

Hyperthyroidism during pregnancy can lead to the following problems in the baby:

  • Low Birth Weight: The child may be born weighing less than 5 pounds and 8 ounces ( less than 2.5 kilograms).

  • Goiter: Hyperthyroidism in the mother during pregnancy can lead to the development of a lump in the thyroid gland of the baby known as goiter.

  • Heart Failure: This can occur due to the baby's rapid heart rate, which may occur due to hyperthyroidism in the mother during pregnancy.

  • Early Closing: Early closing of the soft spot in the baby's skull leads to restricted normal transverse growth of the skull.

How Does Hypothyroidism Affect Pregnancy?

Untreated hypothyroidism during pregnancy can cause the following complication in the mother:

  • Preeclampsia: Dangerously elevated blood pressure after 20 weeks of pregnancy, along with symptoms of kidney and liver dysfunction.

  • Anemia: A reduction in the number of healthy red blood cells (RBC) can lead to anemia in the mother.

  • Gestational Hypertension: Increased blood pressure after 20 weeks of pregnancy with no signs of other organ dysfunction. This condition subsides on its own after childbirth.

  • Placental Abruption: In this pregnancy complication, the placenta separates from the wall of the uterus before birth.

  • Postpartum Hemorrhage: This condition is characterized by excessive bleeding after childbirth. Although it is a rare condition, it can become life-threatening if left untreated. Symptoms of postpartum hemorrhage include vaginal bleeding that does not stop, reduced blood pressure, loss of tone in uterus muscles, etc. It can occur between day one to 12 weeks after childbirth.

  • Myxedema: Hypothyroid coma, or Myxedema coma, is a rare consequence of hypothyroidism. Long-term, untreated thyroid hormone insufficiency causes a decrease in brain function.

An untreated hypothyroidism during pregnancy can cause the following complications in the baby:

  • Infantile Myxedema: It can cause dwarfism (abnormally short statute less than 4 feet and ten inches in adults), low intelligent quotient (IQ), etc.

  • Low Birthweight: The baby will be born weighing less than 5 pounds and 8 ounces.

  • Thyroid Problems: If the thyroid antibodies formed due to Hashimoto's disease cross the placental barrier, the baby can develop thyroid disorders.

How Are Thyroid Conditions Diagnosed During Pregnancy?

The diagnosis of thyroid conditions is made on the following basis:

  • First, a detailed medical history of the mother is taken to check for any history of clinical or subclinical thyroid conditions in the past.

  • A detailed medical history is also made to determine whether any medication taken by the mother could have led to thyroid problems.

  • Family history is also important because if a close family member has a history of thyroid diseases, then the chances of developing thyroid diseases automatically increase.

  • Blood examinations will be done to check for elevated or reduced thyroid hormone levels in the blood. The levels of thyroxine, triiodothyronine, and calcitonin are checked. In addition, levels of the thyroid-stimulating hormone are also checked.

  • The healthcare provider may also check for anti-thyroid antibodies and thyroid-stimulating immunoglobins that are present in the case of Hashimoto's and Graves' disease, respectively.

How Are Thyroid Diseases Treated in Pregnant and Breast-Feeding Mothers?

Treatment for Hyperthyroidism Includes:

  • Usually, subclinical hyperthyroidism does not require any treatment because the condition may be occurring due to excessive vomiting and dehydration, commonly experienced during the first trimester of pregnancy. However, the doctor should closely check the mother's hormone levels.

  • The healthcare provider may prescribe anti-thyroid drugs like Propylthiouracil or Methimazole to reduce thyroid hormone production from the thyroid gland. A very small dosage of these drugs is used during pregnancy.

  • Propylthiouracil has fewer side effects and is less likely to cause birth defects in the baby as compared to Methimazole. However, birth defects occurring as a result of side effects from these anti-thyroid drugs are rare.

  • In rare cases, anti-thyroid drugs cross the placental barrier and enter the baby's bloodstream, causing a low thyroid level in the baby. Therefore, it is very important to prescribe the right dose of medication.

  • Moreover, anti-thyroid drugs can cause several side effects in the mother, including skin rashes, lower immunity, liver damage, sore throat, abdominal pain, fever, jaundice, etc. It is highly recommended to consult the healthcare provider if any of these symptoms are experienced.

Treatment for Hypothyroidism Includes:

  • Subclinical hypothyroidism does not require any treatment, and it should be closely monitored by the healthcare provider.

  • Mothers suffering from hypothyroidism during pregnancy are advised thyroid hormone replacement therapy. This therapy includes the use of the drug Levothyroxine in adequate dosage. Levothyroxine is the replacement for the thyroxine hormone (T4).

What Is Postpartum Thyroiditis?

Inflammation of the mother's thyroid gland after childbirth is known as postpartum thyroiditis. The condition is fairly common and affects one in every 20 women during the first year after childbirth. Postpartum thyroiditis often goes undiagnosed. The symptoms of postpartum thyroiditis are:

  • Initial Hyperthyroidism: Because the thyroid gland is injured and thyroid hormones escape into the blood, the symptoms are initially comparable to hyperthyroidism. It could persist for up to two months.

  • Later Hypothyroidism: Due to the loss of all thyroid hormones, the symptoms later resemble hypothyroidism. This symptom of postpartum thyroiditis might continue for up to a year.

Postpartum thyroiditis occurs as a result of an autoimmune condition of the body, and the doctor will diagnose the condition with the help of clinical examination along with blood tests. Hyperthyroidism occurring in postpartum thyroiditis generally does not require any treatment, but the condition gets better on its own. However, if the symptoms are severe, then the doctor may advise breastfeeding-safe beta-blockers. However, hypothyroidism occurring as a result of postpartum thyroiditis does require treatment, and the doctor will most likely advise thyroid hormone replacement therapy.


Thyroid gland diseases are extremely prevalent during pregnancy in their various forms. However, early diagnosis of these diseases can help in effective and prompt treatment. Although thyroid gland diseases are second to diabetes in the endocrine disorders affecting pregnant women, they can be easily managed. However, the symptoms of thyroid diseases are sometimes very similar to the general symptoms of pregnancy. Therefore, it can get tricky to differentiate between the two. Moreover, thyroid diseases that go unnoticed and undiagnosed and, therefore, untreated end up causing multiple pregnancy complications in the mother as well as the baby.

Dr. Richa Agarwal
Dr. Richa Agarwal

Obstetrics and Gynecology


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