Abstract: Objective To establish the gestational month-specific reference intervals (the first trimester of pregnancy, the second trimester of pregnancy, the third trimester of pregnancy) for free triiodothyronine(FT3), free thyroxine (FT4), thyroid stimulating hormone(TSH)in women in Shijiazhuang area.Methods A total of 412 women in pregnancy based on enrollment guidelines were selected as experimental group. Another 123 normal women without pregnancy served as control group. According to the different periods of pregnancy, 412 pregnant women were sub grouped. Taking 2 ml venous blood from everyone after the physical examination on the next day stored in the procoagulant for centralized testing. Serum samples were used to measure free FT3, FT4 and TSH. All the data were processed for statistical analysis.Results The reference range of FT3 during pregnancy in the trimester, middle and late stage respectively were 3.39-5.97 pmol/L,3.39-5.14 pmol/L,2.91-5.03 pmol/L; The reference range of FT4 during pregnancy in the trimester, middle and late stage respectively were 12.72-18.15 pmol/L,8.81-17.15 pmol/L,6.65-16.82 pmol/L; The reference range of TSH during pregnancy in the trimester, middle and late stage respectively were 1.24-2.46 mU/L,1.46-3.13 mU/L,1.75-3.47 mU/L. According to the standard, the gestational hypothyroidism prevalence rate was 0.5% of the reference values and subclinical hypothyroidism prevalence rate 3.6%, simple hypothyroxinemia prevalence 2.0%, TPOAb positive rate 6.8%.Conclusion The normal range defined in thyroid hormones by the methods for pregnant women in Shijiazhuang area benefits the abnormal disease diagnosis and treatment of thyroid in pregnancy.

Key words: pregnancy, thyroid hormones, fetal development