New developments on the effects of hypothyroidism on pregnancy. This includes several aspects, the first being the effects of subclinical hypothyroidism on the mother and the fetus. The second is the effect of hypothyroxinemia alone on the mother and fetus, including pregnancy outcome and offspring development. Another related topic is the neurointellectual development of offspring born to mothers with subclinical hypothyroidism or simple hypothyroxinemia. There is currently a great deal of controversy in this area, and part of this controversy stems from the fact that many of these studies were conducted when the offspring were younger, which reduces the credibility of IQ tests. In addition, some of the studies have been conducted with insufficient numbers of subjects. There are no randomized controlled studies other than the one we reported in the New England Journal of Medicine a few years ago. Even our own studies have shortcomings in that we start treatment relatively late in women with the disease (at the end of the T1 stage of pregnancy), which is an aspect that I will address in my talk. Related to this is the other question of whether to routinely screen thyroid function in all women in early pregnancy. As of now, there is no good grade A evidence to confirm the need for screening. Research in this area is particularly significant for China, where 50 million newborns are born each year, so it is important to confirm the rationale for routine screening of thyroid function. Current guidelines do recommend so-called “targeted” screening, in which thyroid function is screened in women who are at risk for abnormal thyroid function, such as those with a family history of thyroid disease or other thyroid disorders. But unfortunately applying this screening strategy will result in the underdiagnosis of many women with abnormal thyroid function in pregnancy, which is a big problem and one that brings a lot of controversy. There are also some controversial topics that I did not cover in this talk, such as which tests should be used to assess thyroid function in early pregnancy. Free T4 is not routinely used in the U.S., but in Europe it is routinely measured, and despite the limitations of all the tests, we have found that free T4 testing is a relatively reasonable test. If routine screening is to be carried out, I believe that the basic screening indicator is serum TSH, although the question arises as to what the cut-off value for TSH should be set to. Currently, at least in the US and European guidelines, the upper limit of normal TSH is set at 2.5 mU/L. However, studies in China have shown that the distribution of TSH is different, and if the cutoff value of the US guideline is used, there will be a large group of patients with thyroid hormone deficiency in pregnancy, which may not be consistent with the real situation. I think this suggests that further research is needed in this controversial area, and I also think that the feasibility of further research in China is high because of its large population base and the ability to obtain a sufficient number of cases to conduct randomized controlled studies, which is a very important point. In clinical practice, women go to the obstetrics and gynecology department when they find out they are pregnant. In the UK, for a number of different reasons, blood tests are taken at around 6, 8 and up to 12 weeks of gestation. It would make sense to include TSH in the labs at around 10 weeks, in which case the OB/GYN has a greater role in screening, and if the OB/GYN finds a problem with the indicators of thyroid function, he or she can seek assistance from an endocrinologist. As it stands now, until screening is routinely recommended, I believe that Chinese physicians should be highly vigilant for any thyroid problems in pregnant women. It is important to be aware of not only a family history of thyroid disease, but also a family history of other autoimmune diseases, and any factor that increases the likelihood of developing the disease is a valid reason for testing, i.e., TSH testing. One important group of people, those who have been started on thyroid hormone therapy for hypothyroidism, will need to have their thyroxine dosage adjusted to bring their TSH up to standard during pregnancy.