If the risk value of Down’s syndrome screening, trisomy 21 or trisomy 18 is below 1:270, it is a low risk group and will not be further tested. People with risk values between 1:270 and 1:1000 for trisomy 21 or trisomy 18 are considered to be at critical high risk. There are two methods: method 1: prenatal diagnosis, amniocentesis, amniotic fluid culture, and fetal karyotype analysis for chromosomal abnormalities. Method 2: Noninvasive prenatal test (NIPT), which enriches fetal nucleated (red) cells from the peripheral blood of the pregnant woman to detect fetal DNA, is used to detect fetal chromosomal disorders. Noninvasive prenatal test (NIPT) is a non-invasive test compared to amniocentesis because there is no puncture procedure and the risk of injury, bleeding, infection and miscarriage associated with puncture is avoided. The test is performed between 14 and 24 weeks of gestational age, and the official report is issued after 2 to 3 weeks.