Thyroid Function Tests in the First Trimester of Pregnancy According to Maternal Age in Asia

The American Thyroid Association suggested selective performance of the thyroid function test (TFT) in pregnant women with risk factors such as age over 30 years. We evaluated the limited indication of TFT based on age by analyzing our institution's retrospective data about TFT in pregnant women.

We retrospectively analyzed the results of thyroid stimulating hormone (TSH) and free thyroxine (FT4) with the antithyroid autoantibody test using the Cobas 8000 e801 module (Roche Diagnostics, Mannheim, Germany) performed during the first trimester of pregnancy. Data were analyzed and compared between subjects younger or older than 30 years.

The mean values of TSH and FT4 did not show any significant differences according to age. Also, the two groups had similar prevalence of overt/subclinical hypothyroidism. It was analyzed that over 20% of overt hypothyroidism could be missed by applying age-based screening.

Selective screening according to age (> 30 years) can miss a considerable number of pregnant women with hypothyroidism. Considering the value of appropriate screening and treatment in pregnant women with hypothyroidism, universal screening is necessary rather than selective screening considering the age of pregnant women.