Prenatal screening includes blood tests that are performed during the period of trying to conceive or at the detection of pregnancy, as well as in the 1st and 2nd trimester of pregnancy.
In the latter case, the test involves a combination of ultrasound examination and testing of pregnancy material (such as amniotic fluid obtained by amniocentesis and trophoblast retrieval) and DNA detection. The purpose of the test is to rule out congenital and chromosomal abnormalities of the fetus.