Establishment Of Normal Reference Values Of Thyroid Function During Pregnancy In Handan Area

Objective: To establish the reference intervals of thyroid stimulating hormone(TSH),free triiodothyronine(FT3)and free thyroxine(FT4)in pregnancy of normal pregnant women in Handan area,and to summarize the changes of TSH,FT3 and FT4 in three periods of pregnancy,to compare the levels of TSH,FT3 and FT4 in different ages of pregnant women in the same pregnancy,and to screen the prevalence of hypothyroidism during pregnancy using the diagnostic criteria established in this study.Methods: From June 2018 to October 2019,168 pregnant women who met the acceptance and exclusion criteria of this study were selected from the obstetric clinic of Handan Central Hospital for routine obstetric examination.The serum samples of the three periods of pregnancy were collected successively by the sequential study method.The serum TSH,FT3 and FT4 levels were analyzed by electrochemiluminescence immunoassay.The 95% confidence interval was used to establish the normal reference value range of TSH,FT3 and FT4 in pregnancy.Results: 1.The median and 95% confidence interval of serum TSH in the 1st,2nd,and 3rd trimesters of pregnancy were 1.67(0.09~4.08)mIU/L in the 1st trimester,2.00(0.42~4.18)mIU/L in the 2nd trimester and 2.15(0.48~4.76)mIU/L in the 3rd trimester.There was a significant difference in serum TSH level among the three stages of pregnancy(P < 0.05).The change rule of serum TSH during pregnancy was: 1st trimester < 2nd trimester < 3rd trimester.2.The median and 95% confidence interval of FT3 were 4.88(3.80~7.02)pmol/ L in the 1st trimester,4.12(3.05~5.18)pmol/L in the 2nd trimester,and 3.85(2.81~4.92)pmol/L in the 3rd trimester.There was a significant difference in serum FT3 level among the three stages of pregnancy(P < 0.05).The change rule of serum FT3 during pregnancy was: 1st trimester > 2nd trimester > 3rd trimester.3.The median and 95% confidence interval of FT4 were 17.51(12.79~22.60)pmol/L in the 1st trimester,14.39(10.20~19.09)pmol/L in the 2nd trimester and 12.75(9.47~17.95)pmol/L in the 3rd trimester.There was a significant difference in serum FT4 level among the three stages of pregnancy(P < 0.05).The change rule of serum FT4 during pregnancy was: 1st trimester > 2nd trimester > 3rd trimester.4.There is an inverse correlation between serum TSH and serum FT3,FT4.While there is a positive correlation between serum FT3 and serum FT4.5.The levels of serum FT3 and FT4 in pregnant women of the same gestation period and different ages are different.The levels of serum FT3 and FT4 in the age group of 31-40 are lower than those in the age group of 20-30.6.According to the standard of this study,the prevalence of clinical hypothyroidism and subclinical hypothyroidism were 0.6% and 2.4% respectively.Conclusion: The thyroid function indexes of pregnant women in different gestational period and different age groups are different.It is necessary to establish the specific reference intervals of thyroid function for the effective screening of hypothyroidism in pregnancy.