Thyroid Problems Over-Treated in Pregnancy

New research finds that a doctor's over-treatment of an under-active thyroid during a woman's pregnancy may harm the IQ levels of her growing baby

Thyroid Problems Over-Treated in Pregnancy Piotr Marcinski/Shutterstock

For anyone who has ever had her thyroid levels out of whack, it's no secret how important this butterfly-shaped gland in your neck is when it comes to regulating your metabolism, heart rate, body temperature and many other of your body's crucial functions.

It becomes especially essential for a pregnant woman, whose thyroid levels also affect her unborn child—researchers have found that babies born to mothers who had low levels of thyroid hormones during pregnancy were more likely to have lower IQs and other mental and motor delays later in life. Because of this past research, the American Thyroid Association and the Endocrine Society's guidelines (both written a few years ago) have recommended that doctors treat pregnant women who have a mild form of hypothyroidism.

However, doctors might want to pause before prescribing such medication. The common practice of treating pregnant women with slight thyroid deficiencies could actually cause risks to a fetus as well, according to a new study presented at a recent annual meeting of the Endocrine Society.

Researchers in the Netherlands followed nearly 4,000 mother-child pairs from the fetal stage through young adulthood. During the first or second trimester, each mother's thyroid levels were tested, then, their children received IQ tests or nonverbal performance tasks between the ages of 5 and 8 years. The study authors found that both low and high thyroid levels were associated with low IQ levels. In other words, while women with true hypothyroidism need to be treated during pregnancy and beyond, there's a risk from over-treating women when treatment leads to thyroid hormones on the high side of normal.

Of course, if you're pregnant and concerned you might have hypothyroidism or you already know that you are, talk to your doctor about what's best for you. For instance, some women who were diagnosed with hypothyroidism before pregnancy might need their medication levels adjusted when they're expecting. Your doctor can test to see if your thyroid levels are normal with a simple blood test; then if they're not, you can discuss the next course of action, if any.