There is no specific clinical value on the degree of hypothyroidism that affects the intelligence of pregnant women. It is generally believed that moderate and severe hypothyroidism without standardized treatment throughout pregnancy may affect fetal intelligence. Hypothyroidism, the full name is hypothyroidism, belongs to a variety of causes induced by thyroid hormone synthesis, secretion and biological effects of insufficient endocrine diseases, mild hypothyroidism is generally not much impact on fetal intelligence, moderate to severe hypothyroidism and untreated, easy to lead to fetal intelligence is affected. The central nervous system of the fetus usually starts to grow and develop around the third month of pregnancy, and during this process, if the mother has hypothyroidism, it may lead to the proliferation of brain cells and the development of brain cells to be affected, resulting in the occurrence of cretinism. The danger of hypothyroidism in pregnant women is relatively large, in order to avoid hypothyroidism during pregnancy, it is recommended to control the thyroid function before considering pregnancy.