What is Down syndrome? ================ Down syndrome is a genetic disorder. The main problem of people with Down syndrome is learning disorder. A learning disability can be very mild to very severe. This disorder is sometimes associated with other problems such as heart problems, digestive problems, vision problems, hearing problems, etc. In pregnancy screening for **Down syndrome**, pregnancies that have a higher risk for this disorder are identified and taken care of. In addition to **Down syndrome**, two other genetic disorders can be identified in this screening (Edward syndrome and Patheau syndrome). These two disorders are much rarer than Down's syndrome, but the amount of mezzi disorder in them is very severe and fortunately, they can be identified during Down's syndrome screening. Mother's age is one of the most important factors affecting the probability of the fetus suffering from Down syndrome, and this probability is lower in younger mothers (under 35 years old). Therefore, deciding to get pregnant at a younger age reduces the possibility of getting this syndrome. Screening selectivity Down syndrome screening is optional and based on the decision of the mother. The screening test for Down syndrome is introduced to all pregnant women in the first prenatal care, and if the mother wishes, a midwife or doctor can request a screening test. The mother can opt out of the screening process at any stage. Screening conditions **Down syndrome** screening program is organized for all pregnant women in the country and is carried out in the 11th week to the end of the 13th week of pregnancy (first trimester screening). In cases where the mother, for any reason, decides to perform the screening after the first trimester screening time has passed, Second trimester screening is performed, which is less accurate than first trimester screening and only detects Down syndrome. Screening method The chosen method in our country is combined and single-stage screening. In this method, between the 11th and the end of the 13th week of pregnancy, a special ultrasound called NT ultrasound is performed along with a blood test (to measure serum PAPP-A and Free-Beta) and based on that, the possibility of the fetus suffering from the mentioned disorders is checked. \* Simultaneously performing **blood test and fetal ultrasound** in one day increases the validity of the screening test result. Therefore, it is recommended to do both preferably within 24 hours. If there is no access to NT ultrasound, a method is used in which the blood test is performed in two stages (BHCG, AFP serum measurement in the first trimester and PAPP-A serum measurement in the second trimester of pregnancy) Of course, Unconjugated Estrogen, Inhibin-A, this method is less accurate than the ultrasound method. Interpretation of test results Screening The result of the screening is announced in two ways: positive screening or negative screening. A negative result report by the laboratory means that the probability of infection is so low that there is no need to perform another test. If the result of the screening test is positive, there is a need to perform a genetic diagnosis test for a definitive check. Screening reliability Down syndrome screening by combined method can identify the disease in the fetus with a probability of 85%. Note that the screening test only predicts the probability of the risk of the disease, that is, a positive screening only indicates a higher probability of the fetus being infected and does not indicate the definite infection of the fetus, and this possibility should be checked with genetic diagnosis. Therefore, it is not correct to take any action based solely on the screening result and before the genetic diagnosis test. Genetic testing As said; If the result of the screening test is positive, a genetic diagnosis test is needed for a definitive diagnosis. This work is done by sampling the fluid around the fetus (amniostosis) and testing the genetic material of the fetal cells in this fluid. After examining the cells of the fetus in the genetic diagnosis laboratory, it is diagnosed whether or not the fetus has Down syndrome. The risk of miscarriage following amniocentesis is less than 1 in 100. What is non-invasive prenatal testing (NIPT)? In this method, by taking a blood sample from the mother, it is used to measure the genetic material (DNA) of the fetus in the mother's blood. Although the accuracy of this method is 98-99%, if the screening result with this method is positive, there is a need to perform genetic diagnosis for a definitive diagnosis. This method is mostly used in special cases such as pregnancy at the age of 40 and older, pregnancy with From assisted reproductive methods, it is recommended to have a history of infertility, a history of having a fetus with Down syndrome, or the presence of multiple ultrasound evidences suggesting the possibility of Down syndrome. Deciding whether to terminate or continue the pregnancy If the result of the genetic diagnosis test shows that the fetus has Down syndrome, Considering the many problems that these patients have throughout their lives, the mother can choose to terminate the pregnancy and abort the infected fetus through legal procedures. In this situation, in case of doubt and anxiety, the mother can decide to terminate or continue the pregnancy With the guidance of a gynecologist, refer to a genetics consultant doctor at **Comprehensive Health Services Centers** or by referring to the Association for the Care and Support of Children with Down Syndrome, find out more about the way these children live and care for them. \* Since according to the abortion law, termination of pregnancy is only possible up to 18 weeks and 6 days, it is necessary to carry out the mentioned steps before this time, to terminate the pregnancy in a safe and legal manner. Screening costs When making a decision about screening, ask your doctor about the cost of screening and genetic diagnosis. You need to know that: In general, medical information is confidential and all employees who are considered privy to these secrets and have access to this information must be diligent in maintaining it. The information related to screening is provided to the Ministry of Health and Medical Education in order to evaluate, monitor and improve the screening program in the country by maintaining these principles.