Thyroid Problems and Pregnancy

Pregnant WomanThyroid conditions are extremely common in the United States. It's been estimated that 20 million Americans have some type of thyroid disease, with women being five to eight times more likely than men to develop one. One in eight women will end up having a thyroid disorder at some point in their life. Thyroid conditions can and often do occur in women during pregnancy, which poses the obvious question: can thyroid problems affect a baby's development?

The answer is yes, and expecting mothers need to take extra precaution in making sure their thyroid levels are managed while pregnant. Hypothyroidism and hyperthyroidism, the two most common thyroid conditions, are heavily associated with multiple types of pregnancy and birth complications. Fortunately, with early diagnosis and treatment, there are medications you can take to control your thyroid without posing any risk to your baby. Read more below to find out what these conditions mean, how they affect your baby, and the treatment used to manage symptoms.

What Does a Thyroid do?

The thyroid gland is located on the front of your neck and wraps around the front of your windpipe in a butterfly-like shape. The thyroid plays an important role in making hormones that help your body function. It regulates your body's metabolic rate, muscle control, brain development, bone maintenance, as well as heart and digestive function. It regularly secretes these hormones to keep the body in balance. Thyroid problems are known to be genetic, with 15 to 20 percent of cases of hypothyroidism being caused by inheritance. They can also be caused by mutations in certain genes involved in the production of thyroid hormones.

Thyroid problems usually begin when the gland produces too much or too little hormones. Once this happens, it can be diagnosed as a thyroid disorder. If you develop a thyroid disorder before pregnancy, this would be considered a pre-existing condition. Some mothers develop thyroid problems during their first pregnancy or soon after birth.

Hypothyroidism vs. Hyperthyroidism

There is a wide range of different kinds of thyroid disorders, but hyperthyroidism and hypothyroidism make up the majority of diagnoses. These two conditions primarily focus on the abnormal production of hormones within the gland.

  • Hyperthyroidism: The term "hyper" in hyperthyroidism means "too much". This occurs when the thyroid gland is overactive and begins producing too many hormones. This can accelerate your body's metabolism, resulting in rapid and unusual weight loss coupled with a rapid or irregular heartbeat. There can be several causes of hyperthyroidism, including Graves' disease (an autoimmune disorder that over-stimulates the thyroid), hyperfunctioning thyroid nodules, or thyroiditis. For some pregnant women with hyperthyroidism, they can develop a condition called hyperemesis gravidarum, which is a severe form of morning sickness that causes excessive nausea and vomiting. Other symptoms of hyperthyroidism include:
    • Heart palpitations
    • Tremors in the hands in fingers
    • Thinning skin
    • Fine, brittle hair
    • Excessive sweating
    • An enlarged thyroid gland
    • Increased appetite
    • Changes in menstrual patterns
  • Hypothyroidism: For this condition, "hypo" in hypothyroidism means "too little". The thyroid gland is underactive and not producing enough hormones, which causes bodily functions to slow down. An affected person may have unexplained weight gain or feel unusually fatigued. Hypothyroidism is often caused by an autoimmune disease known as Hashimoto's thyroiditis. With this disease, your immune system's antibodies attack your tissues, including the thyroid. Thyroid surgery or radiation therapy can also cause an underactive thyroid. Symptoms of this condition commonly include:
    • Dry skin
    • Puffy face
    • Muscles weakness
    • Elevated blood cholesterol level
    • Heavier or irregular menstrual periods
    • Slowed heart rate
    • Constipation
Risk Factors for Thyroid Disorders

Some pregnant women are at an increased risk for a thyroid condition during pregnancy. Some of these risk factors are:

  • Currently being treated for a thyroid condition before getting pregnant
  • Having a thyroid condition in the past
  • Previously giving birth to a baby with a thyroid condition
  • Having a family history of autoimmune thyroid disease
  • Having type 1 diabetes
  • Having radiation treatment for hyperthyroidism or other conditions

If you think you're at risk for thyroid disorders during pregnancy, talk to your doctor about your family and medical history to get their opinion on how the disorder will affect your baby. Most thyroid disorders can be successfully managed with the right medications with no adverse effects on the baby.

How can Thyroid Disorders Affect my Baby?

Untreated thyroid conditions can lead to several different complications, before and after birth. This makes it even more important to manage your condition as early as possible.

Complications for pregnant women from hyperthyroidism can include:

  • Preeclampsia: This occurs when a pregnant woman has high blood pressure that causes damage to other organs in the body, most often the liver and kidneys. It usually develops after 20 weeks of pregnancy but can also happen after giving birth (known as postpartum preeclampsia). Preeclampsia can become a potentially fatal condition if left untreated. The condition can cause fetal growth restriction, preterm birth, and cardiovascular disease.
  • Pulmonary hypertension: This is a type of high blood pressure that occurs in the arteries of the lungs and the right side of the heart. Pulmonary hypertension can cause blood clots, arrhythmia, and enlargement of the heart.
  • Placental abruption: This is a serious type of pregnancy complication that can put your baby at risk. The placenta separates from the wall of the uterus during birth and requires immediate medical intervention. Placental abruption can lead to the baby not getting enough oxygen, not getting enough nutrients, premature birth, and in worst cases, stillbirth.
  • Heart failure: This occurs when the heart is not able to pump enough blood to the rest of the body.
  • Thyroid storm: When a thyroid storm happens, the symptoms of hyperthyroidism get much worse. It's rare, but can be life-threatening during pregnancy. A pregnant woman who experiences a thyroid storm is at a higher risk of heart failure.

Newborn complications from hyperthyroidism include:

  • Premature birth: A birth that happens before 37 weeks of pregnancy. A premature baby is at risk of underdeveloped organs, chronic health conditions (such as asthma), and sudden infant death syndrome.
  • Goiter: Abnormal enlargement of the thyroid
  • Low birthweight: A baby born with a low birth rate is at an increased risk for several complications, including infections, jaundice, and respiratory problems.
  • Thyroid problems: A pregnant woman with Graves's disease can have their antibodies cross into the placenta. This can cause the baby to be born with a dysfunctional thyroid.
  • Miscarriage or stillbirth

Pregnancy complications from hypothyroidism differ slightly from hyperthyroidism, but there are some overlapping conditions. 

Complications for pregnant women from hypothyroidism include:

  • Anemia: This condition involves the mother not having enough healthy red blood cells to carry oxygen to the rest of the body
  • Gestational hypertension: This is high blood pressure that occurs during pregnancy but resolves itself after birth.
  • Preeclampsia
  • Placental abruption
  • Postpartum hemorrhage (PPH): This condition causes a woman to bleed heavily after birth. It's rare, but more likely to occur after a C-section. Excessive bleeding can cause a severe drop in blood pressure, which can lead to shock.
  • Myxedema: This a rare but dangerous condition that can develop if hypothyroidism is untreated and allowed to progress into the advanced stages of the disease. It can lead to coma and death.

Newborn complications from hypothyroidism include:

  • Infantile myxedema: This condition is linked to the mother's severe hypothyroidism. It can result in dwarfism and intellectual disability.
  • Low birthweight
  • Problems with the growth of brain and nervous system development
  • Thyroid problems
  • Miscarriage or stillbirth
  • Anemia
How are Thyroid Disorders Diagnosed?

A doctor usually will not test for thyroid anomalies before pregnancy unless a woman is already at risk of developing one. This means an expecting mother should carefully monitor any signs or symptoms that can point to a problem with your thyroid. This can be difficult since some symptoms of thyroid disorders are similar to other harmless conditions. If you feel like you might have a thyroid disorder, a doctor will perform a physical examination and take blood samples to test your thyroid levels. The main things doctors look for in your blood results are the level of thyroid hormones and thyroid-stimulating hormones (TSH). The blood work will be able to confirm the diagnosis of either hypo/hyperthyroidism.

How are Thyroid Disorders Treated?

The primary goal for both types of thyroid disorders is to balance the amount of hormones being secreted throughout the body. There are many medications available that can manage thyroid production. If you have a thyroid condition before getting pregnant, talk to your doctor about whether the medication you're taking is safe for your baby. The doctor may have to adjust your dosage or change the type of medication completely.

Treatment for Hyperthyroidism

Mild hyperthyroidism may not need immediate treatment, as long as it's not presenting any adverse symptoms. Moderate to severe cases will need an anti-thyroid medication. These medications will reduce the amount of hormones being produced. For pregnant women, the timing of these medications is very important. The two main drugs used for hyperthyroidism are called propylthiouracil and methimazole. Propylthiouracil must be used in the first trimester, as it can lead to liver problems if used in the second or third trimester. Methimazole, on the other hand, can only be used after the first trimester. Use of this medication in the first trimester may increase the risk of birth defects. Pregnant women should not use radiation therapy to treat their thyroid condition, because this can lead to the baby also developing a thyroid problem.

Treatment for Hypothyroidism

The main medication used to treat hypothyroidism is called Levothyroxine. This medication replaces the thyroid hormone that isn't being produced enough. Levothyroxine has no adverse effects on your baby and is safe to take throughout pregnancy. For pregnant women who had a prior diagnosis of hypothyroidism, the dosage of your medication may need to be increased. Your thyroid levels can be regularly checked while adjusting the dosage to see what is most effective.


With proper management, thyroid disorders will not put your baby at risk of complications. There are thousands of mothers who have had a successful pregnancy and birth despite having a thyroid condition. The key to having a healthy pregnancy is by meeting with your doctor prior to or shortly after becoming pregnant to begin the necessary steps of treating the problem. Medication is usually the best way to regulate your thyroid levels and fortunately, several drugs are safe to take while pregnant. If you're thinking about getting pregnant and have a pre-existing thyroid condition, speak to your doctor about the best ways to manage your symptoms during gestation.