Early screening for Down’s syndrome is performed at 12-14 weeks of gestation. If you miss the early screening, you can also have a mid-term screening for Down’s syndrome at 16-20 weeks of gestation. Down’s syndrome screening is a blood test to check the concentration of alpha-fetoprotein, estrogen and chorionic gonadotropin in the blood, combined with the gestational week and ultrasound to rule out chromosomal abnormalities causing trisomy 21, trisomy 18, trisomy 13 and other genetic disorders of the fetus. Early screening for Down’s syndrome can be performed at 12-14 weeks of gestation. If the test results are abnormal, chorionic villus puncture can be performed in the early stage of pregnancy, and amniocentesis can be performed in the middle of pregnancy for genetic testing to exclude abnormalities in fetal development. Down’s syndrome screening can prevent the birth of fetuses with congenital diseases and cause heavy burdens to families. It is recommended that pregnant women follow the doctor’s instructions and go to the obstetrics department of the hospital for necessary prenatal checkups and Down’s syndrome screening.