Can you do a Down's screening for drinking water?

If you do Tang screening before drinking water, it is not possible to do Tang screening, because after drinking water to do Tang screening has an impact on the results of the examination. Pregnant women go to the hospital to do Tang screening, so as not to affect the results of the examination. Suggestions: After pregnancy, women must go to the hospital to do Tang screening, to determine fetal development abnormalities, the need to terminate pregnancy.