The specific items include many kinds, and different items have different best examination time. The common clinical teratology examination includes the following three times: 1. NT examination: NT examination is usually performed at 11-13 weeks + 6 days of pregnancy, which can check the thickness of fetal nuchal translucency by ultrasound and determine whether the fetus has malformation, and is the first teratology examination after pregnancy; 2. Pregnant women need to have a blood test at 14-20 weeks + 6 days of pregnancy. Through the blood test of pregnant women, the concentration of alpha-fetoprotein, human chorionic gonadotropin and free estriol in maternal serum is detected and combined with the age, weight and gestational week of pregnant women to determine the risk factor of fetus suffering from congenital stupidity and neural tube defects. If the result of Down’s syndrome screening shows high risk, amniocentesis is needed to further diagnose whether the fetus has malformations; 3. Ultrasound major screening: usually performed at 18-24 weeks of pregnancy, the ultrasound systematically examines various organs of the fetus, such as the heart, limbs, kidneys, spine, head and face, mainly to exclude fetal developmental abnormalities and timely detection of serious lethal and disabling malformations.