Understanding Thyroid Disease in Pregnancy

Contributor: Erik K. Alexander, MD
Erik K. Alexander, MD, is an endocrinologist with the Division of Endocrinology, Diabetes and Hypertension at Brigham and Women's Hospital.

A pregnant woman’s health is essential to the good health of her baby. Expectant mothers should eat well and exercise regularly to reduce the risks of pregnancy complications and potential harm to the developing baby. As a mother-to-be, you should regularly attend prenatal check-ups to keep track of many crucial measures including your weight, blood pressure, and the baby’s heartbeat.

In addition to these more common conditions that are checked during pregnancy, it’s important for you and your doctor to keep track of your thyroid hormone levels. “Various thyroid illnesses can dramatically affect the success of future or ongoing pregnancy,” says Dr. Erik K. Alexander an endocrinologist in the Division of Endocrinology, Diabetes and Hypertension at Brigham and Women’s Hospital.

Common Thyroid Disorders

The thyroid gland, the butterfly-shaped gland at the front of the neck, secretes thyroid hormone – a hormone which helps control metabolism throughout the body. Two common conditions affect the thyroid:

  • Hypothyroidism occurs when the thyroid gland does not produce enough thyroid hormone. A patient with hypothyroidism may gain weight, feel lethargic or tired, and sometimes have hair loss. Treatments include daily intake of a pill containing synthetic thyroid hormone levothyroxine to restore adequate thyroid hormone levels.
  • Hyperthyroidism occurs when the thyroid gland produces too much thyroid hormone. A patient with hyperthyroidism can experience weight loss, shakes or tremors, heart palpitations and possibly hot flashes. Treatments include radioactive iodine therapy to shrink the thyroid gland and slow down production of thyroid hormone, anti-thyroid medication to prevent the production of excessive thyroid hormone, and surgical intervention to remove part of the thyroid gland and reduce production of thyroid hormone.

Thyroid Disease in Pregnancy

During pregnancy, the developing baby depends on the mother to produce thyroid hormone. Too much or too little thyroid hormone production by the mother can cause harm to the fetus. Depending on the mother’s condition the developing baby can suffer in a variety of ways:

A hypothyroid mother has an increased risk of miscarriage early in the pregnancy. There is also an increased risk of potential damage to the fetus’ developing brain, leading to cognitive problems and low IQ.

A hyperthyroid mother has an increased risk of miscarriage. The baby is also at an increased risk of developing Graves’ disease – an immune disorder that results in hyperthyroidism.

Speak to a Medical Professional Early in Pregnancy

Thyroid hormone requirements increase very early in pregnancy, sometimes within the first five to six weeks. Researchers at Brigham and Women’s Hospital have demonstrated an expectant mother’s need for thyroid hormone can increase by about 40 percent during the course of pregnancy to maintain her health and the health of the developing baby. This is especially important for women who do not have a functioning thyroid and are taking medication to treat their thyroid disorder. Dosages are adjusted throughout pregnancy to ensure both the mother and developing fetus receive adequate amounts of thyroid hormone.

“If someone suspects they have a thyroid disorder they should first reach out to their primary care physician or endocrinologist to discuss the issue,” says Dr. Alexander, “this will often lead to a physical examination and blood testing to identify if indeed there is a problem that needs to be treated.”


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