Development of gestation-specific reference intervals for thyroid hormones in normal pregnant Northeast Chinese women: What is the rational division of gestation stages for establishing reference intervals for pregnancy women?

Abstract Background A laboratory- and region-specific trimester-related reference interval for thyroid hormone assessment of pregnant women was recommended. Whether the division by trimester is suitable requires verification. Here, we tried to establish appropriate reference intervals of thyroid-related hormones and antibodies for normal pregnant women in Northeast China. Methods A total of 947 pregnant women who underwent routine prenatal care were grouped via two methods. The first method entailed division by trimester: stages T1, T2, and T3. The second method entailed dividing T1, T2, and T3 stages into two stages each: T1-1, T1-2, T2-1, T2-2, T3-1, and T3-2. Serum levels of TSH, FT3, FT4, Anti-TPO, and Anti-TG were measured by three detection systems. Results No significant differences were found in TSH values between T1-1 group and the non-pregnant women group. However, the TSH value of the T1-1 group was significantly higher than that of T1-2 group ( P P P Conclusion The diagnosis and treatment of thyroid dysfunction during pregnancy should base on pregnancy- and method-specific reference intervals. More detailed staging is required to assess the thyroid function of pregnant women before 20 gestational weeks.