Prenatal diagnosis
From Wikipedia, the free encyclopedia
This article may require cleanup to meet Wikipedia's quality standards.
Please improve this article if you can. (June 2007)
Prenatal testing is testing for diseases or conditions in a fetus or embryo before it is born. The aim is to detect birth defects such as neural tube defects, Down syndrome, chromosome abnormalities, genetic diseases and other conditions. It can also be used to determine the sex of the unborn baby.
Diagnostic prenatal testing can be by invasive methods or non-invasive methods. An invasive method is when probes or needles are inserted into the placenta, e.g. amniocentesis, which can be done from about 14 weeks gestation, and usually up to about 20 weeks and chorionic villus sampling, which can be done earlier (between 9.5 and 12.5 weeks gestation) but which is slightly more risky to the unborn child. Non-invasive methods, called "screens", can only evaluate risk of a condition and cannot determine 100% if the fetus has a condition. Non-invasive techniques include examinations of the mother's womb through ultrasonography and maternal serum screens (i.e. Alpha-fetoprotein) If an abnormality is indicated by a non-invasive procedure, a more invasive technique may be employed to gather more information.
Most often this is performed to test for birth defects. Common procedures include amniocentesis, sonograms, nuchal translucency testing, or genetic screening. The tests can be used to check for conditions such as Down syndrome, spina bifida, cleft palate, Tay Sachs disease, sickle cell anemia, thalassemia, cystic fibrosis, and fragile x syndrome. In some cases, the tests are administered to determine if the fetus will be aborted.
In some cases, fetal screening has been done to determine characteristics generally not considered birth defects. In some parts of the world, if a fetus is determined to be female, it is sometimes aborted. The rise of designer babies and parental selection for specific traits raises a host of bioethical and legal issues that will dominate reproductive rights debates in the 21st century.
