Thyroid Disease in Pregnancy - Pregnancy Complications

The thyroid diseases hyperthyroidism and hypothyroidism are relatively common in pregnancy and important to treat. The thyroid is an organ located in the front of neck that releases hormones that regulate metabolism (the way your body uses energy), heart and nervous system, weight, body temperature, and many other processes in the body.

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During pregnancy, if women have pre-existing hyperthyroidism or hypothyroidism, they may require more medical attention to control these conditions during pregnancy, especially in the first trimester. Occasionally, pregnancy may cause symptoms similar to hyperthyroidism in the first trimester. If anyone experience palpitations, weight loss, and persistent vomiting, they should contact physician.

Untreated thyroid diseases in pregnancy may lead to premature birth, preeclampsia (a severe increase in blood pressure), miscarriage, and low birth weight among other problems.

Causes of Thyroid Disorder during Pregnancy

The most common cause of maternal hyperthyroidism during pregnancy is the autoimmune disorder Grave’s disease. In this disorder, the body makes an antibody (a protein produced by the body when it thinks a virus or bacteria has invaded) called thyroid-stimulating immunoglobulin (TSI) that causes the thyroid to make too much thyroid hormone.

The most common cause of hypothyroidism is the autoimmune disorder known as Hashimoto’s thyroiditis. In this condition, the body mistakenly attacks the thyroid gland cells, leaving the thyroid without enough cells and enzymes to make enough thyroid hormone.

Symptoms of Hyperthyroidism and Hypothyroidism in Pregnancy

a) Hyperthyroidism

Symptoms of hyperthyroidism may mimic those of normal pregnancy, such as an increased heart rate, sensitivity to hot temperatures, and fatigue.

Other symptoms of hyperthyroidism include the following:

Irregular heartbeat
Nervousness
Severe nausea or vomiting
Slight tremor
Trouble sleeping
Weight loss or low weight gain for a typical pregnancy

b) Hypothyroidism

Symptoms of hypothyroidism, such as extreme tiredness and weight gain, may be easily confused with normal symptoms of pregnancy.

Other symptoms include:

Constipation
Difficulty concentrating or memory problems
Sensitivity to cold temperatures
Muscle cramps

Diagnosis of Thyroid Disorder

Hyperthyroidism and hypothyroidism in pregnancy are diagnosed based on symptoms, physical exam, and blood tests to measure levels of thyroid-stimulating hormone (TSH) and thyroid hormones T4, and for hyperthyroidism also T3.

Treatment of Thyroid Disorder

For women who require treatment for hyperthyroidism, an antithyroid medication that interferes with the production of thyroid hormones is used. This medication is usually propylthiouracil or PTU for the first trimester, and if necessary, methimazole can be used also, after the first trimester. In rare cases in which women do not respond to these medications or have side effects from the therapies, surgery to remove part of the thyroid may be necessary.

Hyperthyroidism may get worse in the first 3 months after give birth, and doctor may need to increase the dose of medication (Aleppo, 2015). Hypothyroidism is treated with a synthetic (manmade) hormone called levothyroxine, which is similar to the hormone T4 made by the thyroid.

The doctor will adjust the dose of levothyroxine at diagnosis of pregnancy and will continue to monitor thyroid function tests every 4-6 weeks during pregnancy. If women have hypothyroidism and are taking levothyroxine, it is important to notify doctor as soon as they know they are pregnant, so that the dose of levothyroxine can be increased accordingly to accommodate the increase in thyroid hormone replacement required during pregnancy.

Because the iron and calcium in prenatal vitamins may block the absorption of thyroid hormone in your body, women should not take their prenatal vitamin within 3-4 hours of taking levothyroxine.

Complications of thyroid disease

Uncontrolled hyperthyroidism during pregnancy can lead to

congestive heart failure
preeclampsia—a dangerous rise in blood pressure in late pregnancy
thyroid storm—a sudden, severe worsening of symptom
miscarriage
premature birth
low birth weight

If a woman has Graves’ disease or was treated for Graves’ disease in the past with surgery or radioactive iodine, the TSI antibodies can still be present in the blood, even when thyroid levels are normal. The TSI antibodies she produces may travel across the placenta to the baby’s bloodstream and stimulate the fetal thyroid.

If the mother is being treated with antithyroid medications, hyperthyroidism in the baby is less likely because these medications also cross the placenta. Women who have had surgery or radioactive iodine treatment for Graves’ disease should inform their health care provider, so the baby can be monitored for thyroid-related problems later in the pregnancy.

Hyperthyroidism in a newborn can result in rapid heart rate, which can lead to heart failure; early closure of the soft spot in the skull; poor weight gain; irritability; and sometimes an enlarged thyroid that can press against the windpipe and interfere with breathing. Women with Graves’ disease and their newborns should be closely monitored by their health care team.

Some of the same problems caused by hyperthyroidism can occur with hypothyroidism.

Uncontrolled hypothyroidism during pregnancy can lead to

preeclampsia
anemia—too few red blood cells in the body, which prevents the body from getting enough oxygen
miscarriage
low birth weight
stillbirth
congestive heart failure, rarely

Because thyroid hormones are crucial to fetal brain and nervous system development, uncontrolled hypothyroidism especially during the first trimester can affect the baby’s growth and brain development.

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