ATA News Release 2004

Thyroid Problems May Be a Cause of Very Preterm Delivery; May Warrant Screening

(VANCOUVER, BC, Oct. 1, 2004)—Pregnant women who deliver before 32 weeks may have an underactive thyroid, called hypothyroidism, or thyroid antibodies, which indicates autoimmune thyroid disease, according to a new study being presented on Friday, Oct. 1, at the 76th Annual Meeting of the American Thyroid Association in Vancouver, British Columbia, Canada.

Delivery prior to 37 weeks is called preterm delivery, and delivery prior to 32 weeks is considered very preterm delivery. In the United States, preterm delivery is the number one cause of the death of the newborn and multiple medical problems. The vast majority of these problems occur in babies who are born at less than 32 weeks gestation.

The incidence of preterm delivery is increasing in the United States. In 1987, 10.2 percent of all deliveries were before 37 weeks but, by 1998, the number had increased to 11.6 percent. The Surgeon General has declared that a goal of Healthy People 2010 is to decrease preterm delivery to 7.6 percent. The March of Dimes has also begun a major campaign to decrease preterm deliveries.

“The cause of preterm delivery is not known,” said Alex Stagnaro-Green, MD, Professor of Medicine and Acting Senior Associate Dean for Education at the New Jersey Medical School in Newark. “In general, there is not a way to prevent it. We do know, however, that having a prior preterm delivery is a risk factor for having preterm delivery in the future.”

Therefore, Dr. Stagnaro-Green and colleagues wanted to determine if either thyroid hormonal dysfunction and/or the presence of thyroid autoantibodies in the mother are associated with an increased risk of preterm and/or very preterm delivery. Data were collected prospectively as part of the Camden Study, an ongoing study at the University of Medicine and Dentistry of New Jersey’s School of Osteopathic Medicine, and analyzed as a nested-case control study, in which both cases and controls are selected from within a defined group.

There were 953 women who delivered babies who were enrolled in the study between 1996 and 2002. Blood samples were collected at entry to care, which was around 15 weeks gestation. There were 124 women who had a preterm delivery. A control group of 124 women was selected from among the 829 women who delivered at term, which is considered to be after 37 weeks. All blood samples were assessed for thyroid-stimulating hormone (TSH), thyroperoxidase antibody, and thyroglobulin antibody.

Women with very preterm delivery had an approximate three-fold increase in the risk of having elevated TSH as well as being positive for the thyroglobulin antibody. There were no significant associations between TSH level or thyroglobulin antibody positivity and the risk of moderately preterm or total preterm delivery.

“Whether or not to screen for thyroid disease in pregnancy is extremely controversial,” added Dr. Stagnaro-Green. “Based on our data, I would recommend that all women with a history of preterm delivery be screened for thyroid disease.”

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