I have a thyroid problem. Do I need to know anything special before getting pregnant?

Yes. If you have a thyroid problem, talk with your doctor about your plans for pregnancy. It's important to control the condition with medication before you get pregnant. Certain thyroid conditions may cause difficulty conceiving as well as difficulty maintaining a pregnancy.

About 3 percent of women in the United States have hypothyroidism, in which the thyroid gland doesn't produce enough thyroid hormone. If the condition isn't treated adequately during pregnancy, you'll be at greater risk for complications such as miscarriage, preeclampsia, and preterm delivery.

(Some studies show that children whose mother didn't have enough thyroid hormone during pregnancy have lower IQs. This may be because thyroid hormone contributes to normal fetal brain development.)

About 5 to 15 percent of women of childbearing age have circulating thyroid autoantibodies, which can cause hypothyroidism. If you test positive for these antibodies, your thyroid hormone levels should be checked every four to six weeks during pregnancy to ensure that you don't become hypothyroid during this important time.

The most common treatment for hypothyroidism is levothyroxine, a synthetic form of thyroid hormone. If you're taking this drug, see your doctor before conceiving to make sure you're taking the correct dose. Notify your doctor as soon as you get pregnant, too, because most women need to take a higher dose during pregnancy. (The drug won't harm your baby.)

Learn more about taking medication for hypothyroidism during pregnancy.

Hyperthyroidism – in which the thyroid is overactive rather than underactive – is much less common. It occurs in only about 0.5 percent of women. The most common cause is Graves' disease, an autoimmune condition in which the body produces an antibody that makes the thyroid gland release too much hormone.

Sometimes hyperthyroidism improves during pregnancy. However, if severe hyperthyroidism is not treated during pregnancy, it can lead to miscarriage, maternal heart failure, preeclampsia, premature delivery, or stillbirth, so your doctor will need to monitor you carefully.

Your doctor can help you decide if medication is needed to treat your hyperthyroidism and if you're able to stop taking medication as your pregnancy progresses. (The medications commonly prescribed for hyperthyroidism may cause rare but serious side effects.)

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