After the genome project, many new developments have entered clinical practice. With the introduction of molecular genetic studies into daily practices and the decreasing costs, the use of screening tests as well as in the diagnosis of chromosome and genetic disorders emerges as a separate development. 

 After the genome project, many new developments have entered clinical practice. With the introduction of molecular genetic studies into daily practices and the decreasing costs, the use of screening tests as well as in the diagnosis of chromosome and genetic disorders emerges as a separate development. As a matter of fact, screening tests for Down Syndrome-Trisomy 21, Edward Syndrome-Trisomy 18, Patau Syndrome-Trisomy 13, sex chromosome-X/Y disorders, triploidy, and free DNA measurements from the mother’s blood, originating from the placenta, have entered the field of application. . These screening tests are not diagnostic tests, but they have a sensitivity of close to 99%, although not diagnostic value. Therefore, it differs from other screening tests. The most important difference is that the necessity of CVS or amniocentesis, which is necessary for a definitive diagnosis, is greatly reduced. Thus, the probability of miscarriage of normal pregnancies is significantly and very significantly reduced. 

 In addition to the above situations, the risk can now be calculated with the same fetal DNA test for deletion syndromes that have not been in the screening program until now and do not show any findings with ultrasound. The most common of these syndromes are DiGeorge, 1p36, Angelman, Prader Willi, Cri du Chat. 

 There are the following options for chromosomal disorders, and it would be the best approach for families to choose the most suitable option for them. 

 If a definitive diagnosis is considered, CVS or Amniocentesis should be preferred. In this case, 1/500 pregnancy loss should be taken into consideration. 

Perinatal examination and PAPP-A/beta-hCG blood test at 11-14 weeks of gestation and fetal DNA test in case of risk greater than 1/2500 

Perinatal examination and fetal DNA test at 11-14 weeks of gestation 

If 11-14 weeks of examination period is missed, perinatal examination and quadruple blood test at 15-21 weeks of gestation, and if 1/2500 high risk fetal DNA test 

Perinatal examination and fetal DNA test at 15-21 weeks of gestation