1 500 cases of pregnant women at different trimesters were retrospectively analyzed, including 500 cases in first trimester(<12 weeks), 500 cases in second trimester(13-27 weeks) and 500 cases in third trimester(28 weeks to delivery). 200 healthy non-pregnant women were selected as control group. The serum thyroid hormone levels were tested, such as free 3,5,3'-triiodothyronine(FT3), free thyroxine(FT4), thyroid stimulating hormone(TSH), thyroglobulin antibody(A-TG) and anti-thyroid peroxidase antibody(TPOAb). Statistical analysis were performed.

There was statistical significance between the pregnant group and control group in terms of serum thyroid hormones levels(P<0.05). The morbidity rate of pregnant group was higher(8.53%) than that of control group. The difference among the different trimesters showed statistical significance(P<0.05). From first to third trimesters, TSH levels increased gradually while FT3, FT4 decreased gradually. The positive rates of ATG and TPOAb were 4.6% and 3.6%, respectively for the third trimester, which were lower than first(12.4%, 11.4%) and second trimester groups(9.0%, 8.2%).

There is close relationship between serum thyroid hormones level and trimesters. The pregnant women should be screened for serum thyroid hormones levels and intervened if necessary, in order to achieve better delivery.