The study will recruit 290 pregnant women with gestational age less than 20 weeks. Iodine and selenium condition will be evaluated through dietary recall (on base of Chinese food ingredient information) and biochemical examinations (serum iodine concentrations, urinary iodine concentrations, serum selenium concentrations, etc). The nutritional status of iodine and selenium will be monitored and followed up for all the included subjects throughout the pregnancy. The information of thyroid function and level of anti-TPO and anti-TG will be collected. And all the complications (especially thyroid disease) in pregnancy will also be recorded. All pregnant women will be followed up until the termination of pregnancy, with pregnancy outcomes recorded.
Two hundred and ninety pregnant women with gestational age less than 20 weeks will be recruited in this study. Selenium and iodine conditions, and risk of thyroid disease will be monitored until termination of pregnancy, with pregnancy outcomes recorded.