The health of the baby in the womb is very important for mothers. The health of the unborn baby has been checked since a long time ago. AFP measurement in the mother's blood was used as a fetal anomaly screening test in the periods when ultrasonography was not yet in widespread use and the ultrasound devices used did not have as high resolution as it is today. Afterwards, AFP screening was continued within the scope of the triple test screening developed by adding two substances called HCG and estriol to this measurement and nowadays, AFP measurement is still commonly used within the scope of triple test. When identifying high-risk mothers, the triple test determines the mothers who are at risk for the presence of Down's syndrome and Trisomy 18 in their babies. AFP value in the mother's blood is measured between 16-20 weeks of gestation. This measurement can be made only by AFP (MSAFP) assay or by triple and quadruplicate tests. One of the hormones measured in the triple and quadruple test is AFP. AFP measurement during pregnancy should be done to all pregnant women.If an abnormality can not be detected in the baby by detailed ultrasound examination, amniocentesis should be taken by taking the baby from the amniotic water. AFP (AFAFP) and Acetylcholinesterase (AChE) values are measured in amniotic fluid. The main disease in the baby due to AFP elevation is the anomalies called neural tube defect (NTD). AFP levels are higher in the black race, but NTD is lower in this race. Half of these 46 chromosomes come from the mother and half from the father. Trisomy is the third occurrence of a certain chromosome information in the cells (Trisomy = three chromosomes), which normally comes from one mother and two from the father. This extra chromosome, that is, DNA information, causes overexpression of various genes at the cellular level, not twice, but twice, resulting in abnormalities in the production of various substances. When abnormalities at this cellular level are reflected in the baby's body, we encounter a collection of symptoms called syndromes. Each of the syndromes syndromes has its own characteristics and common features. The most important of these are life-threatening anomalies such as mental retardation and heart and digestive system anomalies. Another common feature is the increased risk of miscarriage, preterm birth, stillbirth and premature newborn death in trisomic infants. Trisomy 18 is responsible for 2% of stillbirth and neonatal deaths and trisomy 13 is responsible for one in 200. Trisomy 18 is an anomaly seen in approximately 6000 live births. The most striking features of most newborn babies are those that are significantly lower in weight than normal birth weights, microcephaly (small head), micrognathia (small jaw), structural abnormalities in the ears and lower ears than normal. Ultrasound is also used to measure the fluid in the baby's nape. This measurement is called “nuchal translucency NT (NT). Since nuchal translucency is known as nuchal translucency, nuchal translucency is commonly referred to as “NT” in the medical literature. In paired test screening, blood biochemical values and neck thickness measurements are evaluated together. For dual testing, the fetus is measured by CRL (crown rump lenght, head-to-butt distance) as well as the nuchal thickness (NT, nuchal translucency). In pregnancy (during pregnancy), the paired combined test is conducted between 11-14 weeks. A paired combined test (also called a combined test) is a combination of the results obtained by measuring B-HCG and PAPP-A levels in the mother's blood test and measuring the nuchal translucency (NT) of the baby. Estriol is the major estrogen in pregnant women. Serial urine and blood levels indicate objective status of fetus and placental function in high-risk pregnant women. Unkonjugated estriol levels are lower than normal if the fetus is small or weak. Maternalestriol levels decrease dramatically before intrauterine fetal death. Considering 9 months of pregnancy in 3 different periods, it is very important and useful for understanding the general development of pregnancy. Trimester is the period in which the organ development of the infant begins and is completed and at the same time the mother's adaptation to the pregnancy occurs. First trimester (first trimester) This is the period in which the organ development of the infant begins and is completed and at the same time the expectant mother is adapting to pregnancy. The second trimester (second trimester) is the period in which the baby continues to develop. The third trimester (last 3 months) is the period when the preparations for birth have begun and finally completed. Every pregnant woman is at risk of carrying a baby with chromosomal disorder in the womb. The higher the maternal age, the higher the risk of chromosomal abnormalities in the baby. The risk of chromosomal abnormalities in the baby increases with advancing gestational age. The majority of babies with anomalies are miscarried in the early stages of pregnancy. These conditions increase the risk of chromosomal disorders.