In clinical practice, it is recommended that pregnant women have thyroid-related tests at 4-8 weeks, and no later than 8 weeks. Thyroid function test is an important program for eugenics, which can assess whether the thyroid function of pregnant women is normal or not, as well as whether there are nodules and lumps in the thyroid gland. Thyroid hormone deficiency not only affects fetal growth and development, but can also affect fetal neurological development, leading to low intelligence levels and the formation of cretinism. Fetal thyroxine does not begin to secrete thyroid hormone until the 12th week of pregnancy, and it is not fully sound until the 20th week, and before the 12th week, it is completely dependent on maternal delivery. Therefore, thyroid function tests should be clarified in a timely manner during pregnancy to ensure normal maternal thyroid function. In addition, it is recommended that thyroid function screening during pregnancy be performed during the preparation period to avoid affecting the neurodevelopment of the fetus during early pregnancy.