Maria Del Pilar Brito, MD, an Assistant Professor of Medicine (Endocrinology, Diabetes and Bone Diseases) at the Icahn School of Medicine

Some of the most frequent questions I get from patients are from women planning to become pregnant who wonder if a thyroid condition is something to worry about.

You should talk with your doctor, because there are a number of steps you can take to protect yourself and your baby.

What you need to do depends upon whether you have an underactive thyroid (hypothyroidism) or an overactive thyroid (hyperthyroidism).

Let’s start with hypothyroidism, a condition in which the thyroid gland doesn’t make enough thyroid-stimulating hormone, also known as TSH. It’s typically diagnosed with a blood test. The most common cause of hypothyroidism is an autoimmune disease called Hashimoto’s thyroiditis.

If you have been diagnosed with an underactive thyroid and are planning to get pregnant, the best course of action is to seek treatment to raise your hormone levels first, before you begin trying to get pregnant. In these cases, I typically prescribe Thyroid Hormone tablets, which contain the same hormone as your body naturally produces.

Once your hormone levels are adjusted, it’s completely safe to become pregnant while continuing to take the hormone pills—often at an increased dose—and you will likely have a normal pregnancy.

If you have been diagnosed with hyperthyroidism, or an overactive thyroid, the situation is slightly different. If your hyperthyroidism is mild, you may not need treatment during pregnancy. We will monitor you carefully, and not treat you unless it becomes necessary. In fact, many patients with an overactive thyroid tend to find this condition quiets down during pregnancy.

The most common cause of hyperthyroidism is an autoimmune disorder called Graves’ disease, which is typically treated with medications, surgery, or radioactive iodine. We don’t administer radioactive iodine to pregnant women, as it can affect the thyroid of the baby. So if treatment is required, we usually use thyroid hormone lowering medications.

It’s important to talk with your doctor because thyroid disorders, if not properly treated, can affect your baby’s neurological development, and there’s a higher risk of miscarriage or preterm delivery in poorly treated patients.

There’s no question we are seeing more and more women who are trying to get pregnant and who are checking their thyroid levels. But that doesn’t necessary mean there is more thyroid disease.

Women having trouble getting pregnant undergo a series of tests, and these may end up showing relatively minor imbalances in thyroid hormone (hypothyroidism or hyperthyroidism) that may have existed for a long time. Normally these patients will be referred to a thyroid specialist who can often reassure them that the thyroid issue is not what has been preventing the pregnancy. However, these patients may still opt for treatment.

One other thing to keep in mind: The thyroid contributes to the development of a healthy baby, which is why we routinely check the thyroid function in pregnant women. But diagnosing a problem can be complicated by the fact that symptoms of thyroid conditions, such as fatigue or weight gain, can resemble those of a normal pregnancy. So it’s best to talk with your doctor if you have any concerns. You can find a lot more information on the website of the American Thyroid Association.

Finally, most women don’t need to worry about passing the thyroid condition along  to their child. Although thyroid diseases run in families, they don’t usually result as a consequence of direct genetic transmission.

Maria Del Pilar Brito, MD, an Assistant Professor of Medicine (Endocrinology, Diabetes and Bone Diseases) at the Icahn School of Medicine at Mount Sinai, is a board certified endocrinologist who sees patients at Mount Sinai Union Square and at The Mount Sinai Hospital.