Does the Down syndrome screening have a moderate risk?

Patient's question:

No

Doctor's answer:

The critical value is 1/250-380, which may vary due to differences in methodology. A value greater than this indicates high risk, while a value lower than this indicates low risk. The probability of having Down syndrome (DS) in the general population under the age of 35 is 1/750. According to the examination time, it is divided into early pregnancy (9-13 weeks) and mid-pregnancy (14-21 weeks).