ObjectiveTo set reference intervals of the levels of thyroid hormones among normal pregnant women without presence of thyroid antibodies during three trimesters of pregnancy in Quanzhou city, Fujian province. MethodsA total of 490 pregnant women during 4-39 week pregnancy without presence of thyroid antibodies were enrolled in Quanzhou city, Fujian province. Levels of thyroid stimulating hormone (TSH), free triiodothyronine (FT3), free thyroxine (FT4) and thyroid peroxidase antibodies (TPO-Ab) were detected through the electrochemistry immunoassay (ECL) method. In addition, a total of 51 healthy women without pregnancy were enrolled to set the reference intervals of levels of thyroid hormones among normal pregnant women without presence of thyroid antibodies. ResultsThe median levels of TPO-Ab were in the reference intervals provided by the pharmaceutical factory. Levels of FT3 and FT4 gradually decreased from the first to the third trimester (P < 0.01), levels of serum TSH gradually increasd from the first to the third trimester (P < 0.01). Compared with those of pregnant women, levels of thyroid hormone in normal non-pregnant women were higher in the first trimester, lower in the second and the third trimesters (P < 0.01). During three trimesters, the reference intervals of FT3 in the three trimesters were (first: 3.75 to 7.23; second 3.31 to 4.9; and third: 3.16 to 4.48 pmol/L); the reference intervals of FT4 were (first: 12.85 to 25.3; second: 12.03 to 20.14; and third: 11.02 to 19.43 pmol/L); and the reference intervals of TSH were (first: 0.01 to 3.79; second: 1.09 to 4.19; and third: 1.08 to 5.95 mIU/L), respectively. ConclusionThrough this detection, we set the levels of thyroid hormones among normal pregnant women without presence of thyroid antibodies during three trimesters of pregnancy in Quanzhou city.