China’s national family planning policy has made the concept of eugenics deeply rooted in people’s minds. How to have a healthy baby has become the central topic of every family preparing for childbirth, which concerns every family and the whole society. Perinatal health care before and after the conception of a fetus actually involves not only the fetus, but also the health and safety of the mother and, more importantly, the quality of the future population of the society. There are many health problems that affect the perinatal period, and thyroid disorders are one of them, including abnormal thyroid function, thyroid tumors and iodine deficiency. Hypothyroidism is also known as hypothyroidism. Clinical hypothyroidism is characterized by both a decrease in FT4 and an increase in TSH, and is often accompanied by significant symptoms such as chills, fatigue, weight gain, and generalized swelling. We call the condition of elevated TSH only as subclinical hypothyroidism, which often has no obvious symptoms. The survey found that 0.8% of women of childbearing age in China are hypothyroid, 5.3% are subclinically hypothyroid, nearly 13% are positive for anti-thyroid peroxidase antibodies (TPO antibodies), and nearly 1% are hyperthyroid. In terms of prevalence, these thyroid disorders are very common problems. The main function of the thyroid gland is to secrete thyroxine, which plays an important regulatory role in human growth, development, and material metabolism, and also plays an important role in the development of intelligence. Congenital or infantile hypothyroidism can lead to cretinism, which manifests as severe mental retardation and growth disturbances. Therefore, screening for hypothyroidism in newborns has become routine in China. Recently, the Endocrine Society of the Chinese Medical Association and the Perinatal Medicine Branch have jointly promulgated the “Guidelines on Thyroid Diseases in Pregnancy and Postpartum”, which provides a standardized document for clinicians in China to diagnose and treat related diseases. The guidelines suggest that in hospitals and maternal and child health institutions where available, it is recommended to screen for thyroid disease early in pregnancy, especially before 8 weeks, and to test for TPO antibodies, thyrotropin (TSH) and free thyroxine (FT4). However, it is a matter of debate internationally whether women who are pregnant should be screened for thyroid disease. This involves is the degree of risk of thyroid disease, whether there are clinical manifestations that can be detected in a timely manner, the prevalence, the cost-effectiveness of screening, and the availability of effective interventions after diagnosis. In terms of disease risk, serious perinatal complications such as maternal miscarriage, hypertension/eclampsia, abnormal fetal development or stillbirth are substantially increased in cases of hypothyroidism. The risk of perinatal complications is also likely to be elevated in subclinical hypothyroidism, and these women have an increased risk of delivering children with low IQ, although consistent findings are still lacking. pregnant women with positive TPO antibodies also have an increased risk of preterm delivery and miscarriage, and some of these women may develop subclinical hypothyroidism or clinical hypothyroidism. Clinical hypothyroidism has the greatest impact on the pregnant woman and the fetus, as it is often diagnosed without difficulty because of the often obvious symptoms. It has become clinical practice to supplement these patients with thyroxine to reduce able perinatal complications. In contrast, subclinical hypothyroidism is not easily detected, and there are studies suggesting that thyroxine supplementation in pregnant women with subclinical hypothyroidism can improve the IQ of their children. However, the need for thyroxine supplementation is still debated internationally due to the lack of large-scale study results. In TPO-positive pregnant women, follow-up may reveal abnormal thyroid function, and some studies also suggest that supplemental thyroid hormone therapy may be beneficial, compared to subclinical hypothyroidism, for which there is even less conclusive evidence. Currently, we usually screen women with risk factors for thyroid disease at the time of planned pregnancy. They are often women with a history or family history of thyroid disease, positive antithyroid antibodies, type 1 diabetes or other autoimmune disease, from iodine deficient/ or iodine over-nourished areas, with goiter, a history of infertility, miscarriage, or pregnant women with neck radiation therapy. If the test results show a TSH > 2.5 mU/L, it is recommended to start a small dose of levothyroxine supplementation (25 micrograms/day), repeat it at 4-6 weeks and titrate the dose to control the TSH below 2.5 mU/L before pregnancy. After pregnancy, thyroid function should be reviewed promptly and levothyroxine dose adjusted. For post-pregnancy hypothyroidism or TSH >10 mU/L, the starting dose of levothyroxine can be 75-100 mcg/day, and for subclinical hypothyroidism, the dose of levothyroxine can be started at 25 mcg/day. The dose of levothyroxine can be adjusted according to the indexes by rechecking thyroid function every 4 weeks. In addition, pregnant women with hypothyroidism who are treated with levothyroxine supplementation may require a 20-30% increase in hormone dosage during pregnancy. However, case finding strategies through screening in these high-risk groups may miss up to 30-80% of the population. For these reasons, our professional academic organizations have made recommendations for early screening “in hospitals or maternal and child health care facilities where available”. This early detection and early intervention is a very positive strategy. It is worth noting that in 2011, the American Academy of Thyroid Diseases used the terms “highly controversial”, “subclinical hypothyroidism and adverse perinatal outcomes have different findings”, “subclinical hypothyroidism with thyroxine treatment intervention results inconsistent,” “results from randomized, multicenter, placebo-controlled trials of subclinical hypothyroidism will not be available until 2015,” and “cost-effectiveness analyses are dependent on the ability of thyroxine treatment to reduce the proportion of low IQ offspring of pregnant women with subclinical hypothyroidism. ” to describe the attitude toward population-wide screening. As can be seen, the question is whether there is a need to screen the entire population and to supplement thyroxine therapy in pregnant women who are subclinically hypothyroid or TPO-positive. However, the scientific evidence to answer this question is still in the process of accumulation.