The reference values of the five thyroid hormones in late pregnancy mainly include: 1. thyroid stimulating hormone (TSH) secreted by the pituitary gland, with a value of 0.3 to 3.0 mIU/L; 2. Triiodothyronine (total T3) with a value of 1.2~3.2nmol/L; 3. tetraiodothyronine (total T4) is 65~156nmol/L; 4. free triiodothyronine (FT3) values of 3.5 to 6.5 pmol/L; 5. Free thyroxine (FT4) value is 11.5~22.7pmol/L. During pregnancy, Thyroid 5 is commonly used to detect the presence of thyroid disorders in pregnant women and the normal development of the fetus. When the thyroid gland bears the function of the corresponding load increased pregnancy, easy to lead to the thyroid reserve is limited or iodine insufficient pregnant women to develop hypothyroidism. Women with normal pre-pregnancy thyroid function but with underlying autoimmune thyroid disease can develop post-partum thyroiditis resulting in clinical thyroid function abnormalities, and similarly it is necessary to have a thyroid function pentameter test in late pregnancy. Therefore, it is recommended that nutrition during pregnancy should be reasonable, timely supplementation of vitamins and trace elements, and increased nutrition will help the development of the mother and fetus. In addition, there should be regular obstetric examination.