Advantages and disadvantages of Down’s syndrome screening: 1, advantages: affordable (a few hundred dollars), non-invasive (only need to take venous blood). 2. Disadvantages: low detection rate and accuracy (even the most comprehensive combined early and mid-term screening can only detect 80-90% of children), high false-positive rate (a large proportion of children with high risk of Down’s syndrome screening are not diagnosed in the end). Advantages and disadvantages of non-invasive NDA: 1. Advantages: non-invasive (only venous blood is needed), high detection rate (99% of children can be detected), low false-positive rate (very few children with high risk of non-invasive screening are not diagnosed). 2. Disadvantages: high cost (more than 2,000 – 3,000 across the country), narrow detection area (currently, the accuracy is high for trisomy 21, 18 and 13, slightly lower for sex chromosomes, and limited for other chromosomes (other chromosomal abnormalities often become high risk in Down screening). (However, non-invasive testing has covered common chromosomal aneuploidy disorders). Advantages and disadvantages of amniocentesis: 1. Advantages: 46 chromosomes can be detected at one time, not only number abnormalities, but also structural abnormalities >10M. In addition, gene chip and single gene disease detection can be performed. High accuracy (the gold standard for chromosomal disease diagnosis) is one of the most extensive and accurate prenatal diagnostic techniques available. 2, disadvantages: there is a certain risk (miscarriage rate 0.5-1%.) In some cases, the cell culture will fail and other tests or re-puncture will have to be done.