Down screening can be done at 15+ weeks. Down screening is a serological marker screening method for aneuploidy chromosome abnormality in mid-gestation. It is a pregnancy screening program that can be performed between 15 and 20 weeks of gestation, which includes a triple screen for alpha-fetoprotein, free beta-human chorionic gonadotropin, and free estriol, and it is mainly used to screen for the risk of the development of the three disorders of trisomy 21-trisomy, trisomy 18-trisomy, and neural tube defects. When the result of the Down screening is low risk, it is necessary to continue to have regular labor and delivery checkups and ultrasound examinations for fetal structural abnormalities, etc., as prescribed by the doctor. When the risk is critical or high, prenatal counseling and prenatal diagnosis are required to further define the condition. Pregnant women with high-risk pregnancies should choose non-invasive prenatal testing or prenatal diagnosis as prescribed by their doctors.