По-английски читаете?It is important to realize that a positive result does not equate to having an abnormality, but rather serves as a prompt to discuss further testing....What is a screening test?It is very important to remember what a screening test is before getting one performed. This will help alleviate some of the anxiety that can accompany test results. Screening tests do not look only at results from the blood test.  They compare a number of different factors (including age, ethnicity, results from blood tests, etc...) and then estimate what a person’s chances are of having an abnormality. These tests DO NOT diagnose a problem; they only signal that further testing should be done.http://www.americanpregnancy.org/prenataltesting/firstscreen.html