Early maternal serological screening is already a free screening program in our province, and it focuses on assessing the risk of certain chromosomal abnormalities and neural tube abnormalities. Fetal chromosomal abnormalities are classified as autosomal abnormalities, sex chromosomal abnormalities and chromosomal translocation aberrations as well as other rare abnormalities. What are the high risk factors? (1) Advanced maternal age: 35 years or older, due to aging or uneven division of oocytes, etc. Trisomy 21 (Down’s syndrome) is most common. (2) Adverse pregnancy history: previous history of chromosomal abnormal fetal pregnancy, the chance of reoccurrence is 1 to 2%. (3) Couples with chromosomal abnormalities: these include abnormal chromosome numbers, or balanced chromosome translocations, which may occur in unbalanced translocations when inherited to offspring. (4) Maternal serologic screening abnormalities: including alpha-fetoprotein (AFP), chorionic gonadotropin (hCG), estriol (E3), and pregnancy-associated protein (PAPP-A), these measurements cannot be used as a single determination and must be considered in conjunction with a variety of conditions such as maternal age. (5) Abnormal ultrasound findings: positive ultrasound findings of certain fetal abnormalities or soft indicators require high suspicion of chromosomal abnormalities. At present, amniotic fluid, chorionic villus or umbilical cord blood puncture and karyotype analysis are the gold standard for confirming chromosomal disorders. In clinical work, it is found that some high-risk pregnant women refuse amniotic fluid or umbilical cord blood puncture, hoping to achieve exclusion through ultrasonography or non-invasive DNA, which will take certain risks and is not scientific. From the more than a dozen cases of Down’s syndrome diagnosed by amniocentesis in our hospital each year, fetal ultrasonography is performed in cases where trisomy 21 has been clearly identified, and less often there is a positive presentation. There are also some chromosomal microdeletions, which are not detected at a high rate due to factors such as the cost of testing.