Assessment of normal range of thyroid function tests in healthy Egyptian pregnant women

Abstract

Background: Gestational thyroid dysfunction has been associated with a variety of adverse pregnancy outcomes. This study aimed to determine trimester-specific reference intervals of thyroid function tests for normal pregnant Egyptian women. Subjects and Methods: A cross-sectional study was conducted at the Obstetric Clinic, Ain Shams University Hospitals. The total enrolled pregnant women were 360, who were divided into the following three groups according to gestational age: Group 1 included 120 participants in the first trimester; Group 2 included 120 participants in the second trimester; and Group 3 included 120 participants in the third trimester. All women were healthy with uncomplicated single intrauterine gestations. A detailed obstetric history, clinical examination, estimation of thyroid-stimulating hormone (TSH), free tetraiodothyronine (FT4), free triiodothyronine (FT3), antithyroid peroxidase antibodies, and thyroglobulin antibodies were done for all participated women. Results: TSH value increased with advancing pregnancy from 1.43 ± 1.16 μIU/mL in the first trimester to 1.78 ± 1.19 μIU/mL in the third trimester, and the difference between each trimester was statistically significant. The FT4 level decreased from 1.16 ± 0.23 ng/dL in the first trimester to 0.98 ± 0.17 ng/dL in the third trimester, and the difference was statistically significant. The FT3 level decreased from 3.18 ± 0.52 pg/ml in the first trimester to 2.79 ± 0.38 pg/ml in the third trimester, and the difference was statistically significant. Conclusion: There were significant changes of thyroid function test during each trimester of pregnancy, the reference ranges in this study are different from previous studies outside Egypt. Accordingly, it is necessary to use trimester specific reference range for every population.