Thyroid conditions present risks for pregnant women and their babies.

Thyroid conditions can, for the most part, be easily managed in day-to-day life with the right medications and hormone therapy. However, the risks of low or high thyroid hormone levels become much more apparent during pregnancy.

Research published in the Endocrine Society’s Journal of Clinical Endocrinology & Metabolism shows that the risk of complications increases for both women with underactive thyroid glands, or hypothyroidism, and those with overactive thyroid glands, or hyperthyroidism. Using data from the Consortium on Safe Labor on 223,512 single-child pregnancies, researchers found that these conditions can increase the risk of obstetrical, labor, and delivery issues.

“Women need appropriate thyroid hormone levels to support a healthy pregnancy, so it is very important to carefully monitor expecting mothers who have thyroid diseases,” said Dr. Pauline Mendola of the National Institute of Health’s Eunice Kennedy Shriver National Institute of Child Health and Development (NICHD) in a press release.

With up to four percent of pregnancies involving thyroid disorders, understanding how to keep the conditions in check is crucial for both mother and child.

“In the United States, at least 80,000 pregnant women each year have thyroid diseases,” said the study’s lead author, Dr. Tuija Männistö of the NICHD, in a press release. “These women are at increased risk of having serious adverse pregnancy outcomes, including hypertension and preterm birth. They also have a higher rate of labor inductions and other birth interventions.”

Women require an increase in thyroid hormones during pregnancy, and many who are using the synthetic hormone levothyroxine need to boost their doses early in pregnancy. However, these hormonal changes can then lead to hypothyroidism. The researchers found that up to 60 percent of women treated with the levothyroxine had elevated levels of thyrotropin, the thyroid-stimulating hormone.

This points to the need for improved dose adjustments for pregnant women with thyroid conditions. According to the study, “Poor control of hyperthyroidism during pregnancy is also associated with increased risk of miscarriage and stillbirth, hypertension in pregnancy, preterm births, and maternal heart failure.”

More research needs to be done to improve thyroid disorder treatment, but researchers know in which direction they need to move.

“Although we lacked information on treatment during pregnancy, these nationwide data suggest either a need for better thyroid disease management during pregnancy or that there may be an intrinsic aspect of thyroid disease that causes poor pregnancy outcomes,” the study authors wrote. “Future research is still needed to distinguish if women with adequately treated thyroid disease have higher risk of pregnancy complications due to the disease itself or if treatment can truly prevent adverse outcomes.”

As for whether women with thyroid conditions should rethink pregnancy, Mendola has reassuring advice.

“Although they were more likely to have obstetric complications than women without thyroid disease, it is important for individual women to know that most women with thyroid disease in our study did not experience complications,” she said. “More research is needed to identify ways to further reduce their risk, and careful monitoring of thyroid function during the course of pregnancy may be helpful.”

Information on thyroid dysfunction during pregnancy can also be found in The Endocrine Society’s clinical practice guidelines.