An Underactive Thyroid Causes Pregnancy Complications | Fit Pregnancy

Should You Test for an Underactive Thyroid?

It’s been linked to miscarriage, preterm birth and developmental delays. Why aren’t more OBs screening expectant moms?


Located in your neck, the thyroid gland produces hormones that affect metabolism, breathing, heart and nervous system functions, body temperature and more. During your pregnancy, your baby is entirely dependent on receiving thyroid hormone—which plays a large role in fetal brain and nervous system development—from you for the first trimester.

“In essence, pregnancy is a stress test for the thyroid,” says endocrinologist Alex Stagnaro-Green, M.D., the lead author of guidelines on thyroid management during pregnancy from the American Thyroid Association (ATA). “The body has to produce about 50 percent more thyroid hormone during pregnancy.”

Often, the thyroid is up to the task. However, a study of half a million pregnant women in 2012 found that 15 percent of pregnant women had heightened levels of thyroid stimulating hormone, or TSH.

Higher-than-normal TSH levels are an indicator of an underactive thyroid, referred to clinically as hypothyroidism. This finding comes as research mounts suggesting that too-little thyroid hormone increases the chances of miscarriage, preterm delivery and mental retardation in children—causing some experts to question whether all pregnant women should have their thyroid function tested. Pregnant women with low thyroid hormone can be safely treated by taking a daily thyroid hormone supplement.

Are you at risk?

Experts agree that certain women should have their thyroid function tested early in pregnancy. They include women with a personal history of thyroid disease; a strong family history of thyroid disease; an autoimmune disease such as type I diabetes or lupus; previous radiation to the neck or symptoms of an under- or overactive thyroid.

“Extreme fatigue, weight gain and feeling cold all the time are the main symptoms to watch for,” says maternal-fetal medicine specialist Sarah J. Kilpatrick, M.D., PH.D., former chairwoman of the American College of Obstetricians and Gynecologists’ Committee on Obstetric Practice. She and the college maintain that if none of this applies to you, there is no reason to check your thyroid.


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