BackgroundEstablishment of trimester- and assay-specific reference intervals for every population is recommended. The aim of this study was to establish a trimester- and assay-specific reference interval for thyroid-stimulating hormone (TSH) and free thyroxine (FT4) in Korean pregnant women.MethodsFrom April 2012 to December 2012, 531 pregnant women receiving prenatal care and 238 age-matched, non-pregnant women were enrolled in this study. After excluding patients with pregnancy-associated complications or thyroid-specific autoantibody, 465 pregnant and 206 non-pregnant women were included. Non-parametric analysis (2.5-97.5th percentile) was performed to determine the reference interval. Levels of TSH and FT4 were determined by electrochemiluminescence immunoassay (Elecsys thyroid tests, Roche Diagnostics, Germany).ResultsThe TSH reference intervals were 0.01-4.10, 0.01-4.26, and 0.15-4.57 mIU/L for the first, second, and third trimester, respectively. From the first trimester to the third trimester, the median TSH levels showed a significantly increasing trend (P<0.0001). The FT4 reference intervals were 0.83-1.65, 0.71-1.22, and 0.65-1.13 ng/dL for the first, second, and third trimester, respectively, showing a significantly decreasing trend (P<0.0001).ConclusionsEstablishing trimester-specific reference intervals in pregnant women is essential for accurate assessment of thyroid function. Our population-specific and method-specific reference intervals will be useful for screening Korean pregnant women for thyroid disease.

Our study presents a formal characterization of PEth blood concentrations for screening alcohol ingestion in first-trimester pregnant women. However, caution is recommended for overrepresenting either negative or positive results.

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PEth-16:0/18:1 was detected in pregnant women at 4-6 weeks after their last low-to-moderate alcohol ingestion, and therefore appears to be a reliable biomarker of prenatal alcohol exposure to study the teratogenicity of alcohol at these exposure levels.