The prenatal procedure by which a sample of fetal cells is drawn from the fluid surrounding the fetus is called amniocentesis or chorionic villus sampling (CVS). The embryonic cells of fetus are tested to ensure that the fetus is having no genetic defect, or any abnormality in the body development. This procedure is mostly opted to screen for polyploidy, i.e, the presence of abnormal numbers of chromosomes in the cells of the fetus. The whole process of doing these tests is called, a prenatal genetic screening test (PGS).
