Things Every Mother Should Know

The Thyroid, Infancy, and Pregnancy

Why is it important to take care of the thyroid during pregnancy?

Even before conception, thyroid conditions that have lingered untreated can hinder a woman’s ability to become pregnant or can lead to miscarriage. Fortunately, most thyroid problems that affect pregnancy are easily treated. The difficulty lies in recognizing a thyroid problem during a time when some of the chief complaints — fatigue, constipation, and heat intolerance — can be either the normal side effects of pregnancy or signals that something is wrong with the thyroid.

Although detecting a thyroid problem is important, it is equally necessary for those already diagnosed with a condition to have the thyroid checked if they are planning to become pregnant or are pregnant.

Thyroid hormone is necessary for normal brain development. In early pregnancy, babies get thyroid hormone from their mothers. Later on as the baby’s thyroid develops it makes its own thyroid hormone. An adequate amount of iodine is needed to produce fetal and maternal thyroid hormone. The best way to ensure adequate amounts of iodine reach the unborn child is for the mother to take a prenatal vitamin with a sufficient amount of iodine. Not all prenatal vitamins contain iodine, so be sure to check labels properly.

Who should be tested?

Despite the impact thyroid diseases can have on a mother and baby, whether to test every pregnant woman for them remains controversial. As it stands, doctors recommend that all women at high risk for thyroid disease or women who are experiencing symptoms should have a TSH and an estimate of free thyroxine blood tests and other thyroid blood tests if warranted. A woman is at a high risk if she has a history of thyroid disease or thyroid autoimmunity, a family history of thyroid disease, type 1 diabetes mellitus, or any other autoimmune condition. Anyone with these risk factors should be sure to tell their obstetrician or family physician. Ideally, women should be tested prior to becoming pregnant at prenatal counseling and as soon as they know they are pregnant.

Hypothyroidism during pregnancy

When a woman is pregnant, her body needs enough thyroid hormone to support a developing fetus and her own expanded metabolic needs. Healthy thyroid glands naturally meet increased thyroid hormone requirements. If someone has Hashimoto’s thyroiditis or an already overtaxed thyroid gland, thyroid hormone levels may decline further. So, women with an undetected mild thyroid problem may suddenly find themselves with pronounced symptoms of hypothyroidism after becoming pregnant.

What are the risks of an underactive thyroid gland during pregnancy?

In the United States, most women who develop hypothyroidism during pregnancy develop mild disease and may experience only mild symptoms or sometimes no symptoms. However, if you had a mild, undiagnosed condition before becoming pregnant, the condition may worsen. A range of signs and symptoms may be experienced, but one needs to be aware that these can be easily written off as normal features of pregnancy. Untreated hypothyroidism, even a mild version, may contribute to possible pregnancy complications. Treatment with sufficient amounts of thyroid hormone replacement significantly reduces the risk for developing any of the following pregnancy complications associated with hypothyroidism:

Abruptio placentae
Premature birth
Postpartum hemorrhage
Preeclamsia
Anemia
Miscarriage

Treating hypothyroidism during pregnancy

There is no difference between treating hypothyroidism when a woman is pregnant than when she isn’t. Levothyroxine sodium pills are completely safe for use during pregnancy. They will be prescribed in dosages that are aimed at replacing the thyroid hormone the thyroid isn’t making so that the TSH level is kept within normal ranges. Once a woman begins taking thyroid hormone pills, she will be monitored closely until her TSH level is within normal ranges. Once it is, the doctor should check TSH levels every six weeks or so. The physician may also counsel patients to take their thyroid hormone pills at least one-half hour to one hour before or at least three hours after they take iron-containing prenatal vitamins or calcium supplements, both of which can interfere with the absorption of thyroid hormone.

Hyperthyroidism during pregnancy

Graves’ disease tends to strike women during their reproductive years, so it should come as no surprise that it occasionally occurs in pregnant women. Reports on pregnancies lasting longer than twenty weeks suggest that Graves’ disease occurs in 2 per 1,000 pregnancies or 0.2 percent of all pregnancies. Pregnancy may worsen a preexisting case of Graves’ disease. Graves’ disease can also emerge for the first time, typically during the first trimester of pregnancy. The disease is usually at its worst during the first trimester. It tends to then improve in the second and third trimesters and flare up again after delivery.

What are the risks of an overactive thyroid during pregnancy?

A woman with hyperthyroidism while pregnant puts her at an increased risk for experiencing any of the signs and symptoms of hyperthyroidism. And unless the condition is mild, if it is not treated promptly, a woman could miscarry during the first trimester; develop congestive heart failure, preeclampsia, or anemia; and, rarely, develop a severe form of hyperthyroidism called thyroid storm, which can be life threatening.

Hyperthyroidism, if untreated, can lead to stillbirth, premature birth, or low birth weight for the baby. Sometimes it leads to fetal tachycardia, which is an abnormally fast pulse in the fetus. Women with Graves’ disease have antibodies that stimulate their thyroid gland. These antibodies can cross the placenta and stimulate a baby’s thyroid gland. If antibody levels are high enough, the baby could develop fetal hyperthyroidism, or neonatal hyperthyroidism.

How is hyperthyroidism diagnosed during pregnancy?

As with hypothyroidism, diagnosing hyperthyroidism based on symptoms can be tricky because pregnancy and hyperthyroidism share a host of features. Still, one should be aware of the symptoms and bring them to the attention of a doctor if they are experiencing them. For instance, feeling a heart flutter or suddenly becoming short of breath, both symptoms of hyperthyroidism, can be normal in pregnancy, but a doctor still may want to investigate these symptoms. An individual with any risk factors for thyroid disease should make certain they are tested.

While hyperthyroidism can easily be diagnosed through blood tests, finding out what’s causing it may require scanning tests that use minimal amounts of radioactive iodine. During pregnancy, however, scanning tests are not done because small amounts of radioactivity may cross the placenta and become concentrated in the baby’s thyroid gland. Antibody tests can be used to distinguish Graves’ disease from other causes. A physical exam can help diagnose or distinguish a toxic adenoma or toxic multinodular goiter.

Treating hyperthyroidism during pregnancy

Very mild hyperthyroidism usually does not require treatment, only routine monitoring with blood tests to make sure the disease does not progress. More serious conditions require treatment. However, treatment options are limited for pregnant women. Radioactive iodine, which is typically used to treat Graves’ disease, cannot be used during pregnancy because it easily crosses the placenta, potentially damaging the baby’s thyroid gland and causing hypothyroidism in the baby.

Due to its potential risks, the goal of treatment is to use the minimal amount of antithyroid drugs possible to maintain a patient’s T4 and T3 levels at or just above the upper level of normal, while keeping TSH levels suppressed. When hormones reach the desired levels, drug doses can be reduced. This approach controls hyperthyroidism while minimizing the changes of a baby developing hypothyroidism.

Thyroid diseases in children

Thyroid problems are much less common in children than adults, but when they strike, they can be more worrisome because of their potential effect on children’s growth and developing brains. In adults, treatment usually reverses the effects of thyroid diseases, even when they go undetected for years. Yet in early childhood, hypothyroidism can lead to permanent mental deficiencies and short stature if it is not treated promptly. Hyperthyroidism can lead to accelerated growth in children, and when it affects infants, it can be fatal. Thanks to screening programs that test all newborns for hypothyroidism, the immutable effects of that disease are prevented in numerous children. Each year, in North America alone, more than five million newborns are screened annually, and hypothyroidism is detected and treated in fourteen hundred of these infants.

A child may be born with a thyroid condition or may develop one sometime during childhood. Diagnosing thyroid diseases that aren’t detected through screening programs can be especially tricky, since it is up to the parent to recognize when something is wrong. This certainly isn’t easy when dealing with young children who aren’t talking yet or with older children who may not be able to describe what they feel—or even know what they are feeling isn’t normal.

If you or someone in your family has a thyroid condition, your child may be at a higher risk for developing a thyroid disorder.