Results of the study, to be presented Jan. 17 at the annual meeting of the Society for Maternal-Fetal Medicine in New Orleans, showed that babies born to women with overactive or underactive thyroid also were at increased risk of a variety of other anomalies, including cleft lip or palate, or extra fingers. In addition, infants born to women with underactive thyroid were at increased risk of cardiac problems even if the mothers were on medication.
The research contradicts some earlier studies indicating thyroid disease did not pose fetal risks, but those studies were conducted using less sophisticated technology for detecting birth defects, says David A. Nagey, M.D., Ph.D., study co-author and associate professor of gynecology and obstetrics.
"We already knew that there was an increased risk of problems, mostly intellectual or developmental, in children as a result of hypothyroid (underactive thyroid) pregnancies, but the link with birth defects is new and unexpected," Nagey says. "If these results are confirmed, it could lead to routine testing of women for thyroid disease prior to pregnancy and for cardiac anomalies in the fetuses of women with hypothyroidism."
Nagey recommends that doctors consider thyroid testing during a woman's pre-pregnancy consult or add it to the routine prenatal diagnostic tests. If the test indicates the woman has hypothyroidism, a fetal echocardiogram during the 20th week of pregnancy might be warranted.
The researchers studied 101 women (64 with hypothyroidism and 50 with the overactive version, hyperthyroidism) who gave birth at The Johns Hopkins Hospital between December 1994 and June 1999. The women's average age was 31; very few admitted to smoking, drinking alcohol or
Contact: Karen Blum
Johns Hopkins Medical Institutions