Thyroid structure, function and iodine status by pregnancy trimester in Harbin, China

Background and Objectives: Thyroid disease in pregnancy can have devastating effect on the fetus. In Harbin, China, there is insufficient knowledge about the incidence of and contributing factors to thyroid disease in pregnancy. This study investigates whether urine iodine concentration (UIC), as a proxy for iodine intake, affects the thyroid structure and/or function during each trimester. Methods and Study Design: Data of 24000 pre-pregnant women were collected from January 2017 to August 2019. Serum thyroid hormone levels were measured, and thyroid ultrasonography was performed. If thyroid ultrasonography and thyroid function findings were normal before pregnancy and were abnormal after pregnancy, the current gestational age was recorded and the UIC was measured. Finally, a total of 500 participants were included in the study. Results: There were significant differences in the incidence of abnormal thyroid structure and function between trimester groups (p