Objective To survey the thyroid-hormone changes in gravidas,and to establish the reference intervals for thyroid-hormones in each trimester of normal pregnancy in Pingdingshan.Methods 2 645 gravidas who established documents in our hospi-tal were enrolled,The gravidas were divided to different groups by age (≤30 and >30 years old)and 425 cases of early pregnancy women,1 657 cases of middle pregnancy women and 563 cases of late pregnancy women were collected as research group.4 kinds of thyroid functions in the six groups were detected by electrochemical luminescence.Results FT3 and FT4 gradually reduced as the growth of the pregnancy period,but TSH and TPOAb increased.There is statistical difference in all thyroid-hormones between all trimesters of pregnancy and different age groups.Conclusion There is significant difference in thyroid-hormones for different sta-ges of pregnancy and different age groups.Therefore,establishing reference intervals of thyroid-hormones during different stages of pregnancy may be important for clinical practice.