Diagnostic Value and Thyroid Hormone Variations in Pregnant Women During Pregnancy in Hui'an County in China.

To evaluate the diagnostic value of thyroid hormones in pregnancy-related thyroid conditions and ascertain the reference range of thyroid hormones in Hui'an pregnant women. We examined 760 pregnant women (406 early, 172 mid, and 182 late pregnancy) and 114 non-pregnant controls. A 95% medical reference range was computed based on measurements of thyroid hormone levels (FT3, FT4, and TSH). Group comparisons were conducted, and the diagnostic accuracy was assessed using ROC curves. There were significant differences in thyroid hormone levels between pregnant women at different stages and non-pregnant women (P < 0.05). In contrast to mid-pregnancy and controls, FT3 and FT4 were higher in the early and late stages of pregnancy (P < 0.05), although TSH was decreased during pregnancy. Compared to healthy or hypothyroid pregnant women, the diagnostic positive rate for hyperthyroidism was greater (P < 0.05). TSH, FT3, and FT4 had larger AUCs in ROC analysis for identifying hyperthyroidism than hypothyroidism (P < 0.05), and the combination of these markers improved diagnostic accuracy (P < 0.05). In Hui'an, thyroid hormone levels vary over the weeks of pregnancy and between pregnant and non-pregnant women. By establishing local reference ranges, thyroid problems in pregnancy can be diagnosed, and complications can be avoided.