Underactive thyroid common in moms-to-be

About 15 percent of pregnant U.S. women tested positive for gestational hypothyroidism -- underactive thyroid -- higher than prior estimates, researchers say. Scientists at Quest Diagnostics conducted a study of 502,036 pregnant women and analyzed the prevalence of hypothyroidism during pregnancy, using clinical guidelines issued by the American Thyroid Association. The study, published online ahead of the March print edition of the Journal of Clinical Endocrinology & Metabolism, found one in six pregnant women tested were positive for gestational hypothyroidism, or underactive thyroid during pregnancy, under new clinical guidelines for detecting the disorder. The study also found: -- Women ages 35-40 are 1.8 times as likely as those ages 18-24 to develop gestational hypothyroidism. -- Women weighing over 275 pounds are 2.5 times as likely as those weighing 100 to 124 pounds to develop gestational hypothyroidism. -- Asian women had a higher positivity rate than other major ethnic groups for gestational hypothyroidism. -- Asian women are almost five times as likely as African-American women to develop gestational hypothyroidism. \"Our findings should re-invigorate the medical community\'s longstanding debate about the best approach to clinical assessment and management of thyroid function during pregnancy,\" Dr. Jon M. Nakamoto, medical director for Quest Diagnostics, Rady Children\'s Hospital and the University of California, San Diego, said in a statement.