Journal of Genetic Syndromes & Gene Therapy
Open Access

Difference between Screening Test and Prenatal Genetic Test

John Tang^{* *}Correspondence: John Tang, Department of Obstetrics and Gynaecology, University of Ghana Medical School, Ghana, China, Email:

Author info »

Description

To find out if a fetus has certain abnormalities, such as some hereditary or spontaneous genetic illnesses, prenatal diagnostic testing entails evaluating the fetus before birth (prenatally). The risk of genetic defects in the fetus can be estimated with the use of ultrasonography and the measurement of specific substances in the pregnant woman's blood. It is possible to perform these blood tests plus an ultra-sonogram as part of standard prenatal treatment. Doctors may do procedures to analyze the genetic makeup of the fetus, such as amniocentesis and chorionic villus sampling if the findings of these tests point to an elevated risk. These genetic examinations are invasive and carry certain dangers for the developing fetus. Some prenatal diagnostic procedures, including blood testing and ultrasound, are frequently a component of standard prenatal care. Blood testing and ultrasonography are chorionic villus sampling, amniocentesis, and percutaneous umbilical blood sample are examples of more invasive prenatal genetic tests that are sometimes necessary but are generally safe. These more intrusive tests are typically carried out when a parents who has a chromosomal or genetic abnormality (such as a defective neural tube). However, a lot of doctors provide this kind of testing to all expectant mothers, and any expectant mother can ask for it. these tests do have some hazards, especially for the fetus. Prenatal testing may be provided to expectant mothers to ascertain whether there is a chance that the fetus will be born with a genetic disorder or birth defect. Prenatal testing may help select various pregnancy alternatives or unique management of the pregnancy and birth to improve the baby's prospects.

Depending on the illness being tested for and the trimester of pregnancy the mother is in, there are various prenatal testing options. An overview of the many prenatal tests that may be provided to expectant women is provided in this appendix.

Screening test

Both the first and second trimesters of pregnancy allow for the use of screening tests. A blood sample from the mother and an ultrasound examination are both required for first-trimester screening, but only a blood sample is needed for second-trimester screening. First and second-trimester screenings may also be done for some women, a practice known as "integrated" or "combined" screening. The likelihood of certain chromosomal disorders in the present pregnancy is then estimated using the blood test and ultrasound data in conjunction with mother characteristics like age and weight. Diagnostic testing is provided to patients who have a positive screening result, which is often accessible within a week. Depending on the test type used, different screening tests have different detection rates. The only way to know for certain is a diagnostic test is needed to determine or a infant has a chromosomal abnormality.

Cell free DNA

The tiny amount of DNA that is released into a pregnant woman's bloodstream by the placenta is known as cell-free DNA. It is possible to check for Down syndrome, Edwards syndrome, Patau syndrome (trisomy 13), and issues with the number of sex chromosomes in a sample of a woman's blood that contains cellfree DNA. Starting at 10 weeks of pregnancy, this test can be performed. The results take roughly a week to come in. If the cell-free DNA test is positive, an amniocentesis or CVS diagnostic test should be carried out. Using a blood sample or tissue sample swabbed from the inside of the cheek, carrier screening is performed on parents (or those who are only considering becoming parents). These tests are used to determine a person's gene susceptibility to specific inherited diseases. Both before and during pregnancy can be used for carrier screening. Prenatal genetic screening tests of the pregnant woman's blood and the outcomes of ultrasound scans can all be used to identify aneuploidy, neural tube abnormalities (NTDs), and some deformities of the abdomen, heart, and facial features in the fetus. The tests are the main topic of this FAQ. They consist of cell-free DNA testing, second-trimester screening, combined firstand second-trimester screening, and first- and second-trimester screening alone.