Study on the establishment of trimester-specific reference intervals of thyroid hormones for pregnancy under normal iodine intake

Objective To establish trimester-specific reference intervals of thyroid hormones for pregnancy in normal iodine intake. Methods A total of 716 pregnant women were selected as research subjects, and another 307 normal women without pregnancy were served as control group.The serum thyroid stimulating hormone(TSH), free thyroxine(FT4), free three iodine thyroid gland originalacid(FT3) were measured by chemiluminescent microparticle immunoassay.The changes of thyroid indicators in different gestational period were analyzed, and the thyroid reference range during pregnancy was established. Results The levels of TSH, FT3 and FT4 in non-pregnant women and women in different pregnancy were significantly different(F=78.901, 249.571, 137.090, all P 0.05). However, the difference among the three diagnostic criteria for subclinical hypothyroidism was statistically significant(χ2=9.661, P<0.05). Conclusion The thyroid function indicators of pregnant women are significantly different from those of normal people, and there are differences in different stages of pregnancy.Establishing a region-specific reference range can effectively prevent misdiagnosis or missed diagnosis of thyroid disease and reduce adverse pregnancy outcome. Key words: Pregnancy; Thyroid stimulating hormone; Free thyroxine; Free triiodothyronine