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Prenatal Testing

What is genetic testing?

To preface, genetic testing is a way for doctors to locate absent or defective genes, according to kidshealth.org. This information can then be used to inform the patients if they have a certain medical condition. Prenatal genetic testing takes place before the baby is born and is done for the purpose of knowing if a baby will have disorders. Many bodily fluids, as well as tissues, can be used for testing, but the type of test depends on what type of genetic disorder the doctor is looking for.

Image is courtesy of geneticliteracyproject.org.

What does prenatal testing look like?

Blood tests can be done for pregnant women searching for the possibility of some disorders such as down syndrome. To find specific disorders, the doctor might suggest an amniocentesis or chorionic villus sampling (CVS). Both of these tests are done within the second trimester.


As Merck Manual states, amniocentesis allows the doctor to measure the level of alpha-fetoprotein, a protein produced by the baby, in the amniotic fluid found in the sac that surrounds the fetus. This process is completed to find out if the fluid contains the enzyme acetylcholinesterase. High levels of alpha-fetoprotein in the fluid may indicate a neural tube defect or abnormalities in other structures in the body. An increase in alpha-fetoprotein and acetylcholinesterase may demonstrate a neural tube defect like spina bifida.


This test takes place when the doctor removes a piece of the placenta as a way to check for genetic problems.

*Both the amniocentesis and CVS tests are invasive, so they may present a small risk of having a miscarriage.

When is testing recommended?

Prenatal testing can be recommended if a new mother is over the age of 35. If a pregnant woman is over this age, her chances of having children with a chromosomal issue increase. Kids of older fathers are in danger of developing new dominant mutations, which are induced by a single deficiency that hasn't previously taken in the family. Doctors might also recommend another test if a previous test indicated an abnormal result. Other reasons could include having a hereditary disorder, two or more miscarriages, and if the parent already has a child with a birth defect.

The Future of Prenatal Testing

According to the National Human Genome Research Institute, now, pregnant women no longer have to go through invasive procedures to diagnose their children. Recently, efficient methods for DNA sequencing which investigate DNA in the mother's blood have become available to women during the first trimester of pregnancy, with no risk of miscarriage. This process is called non-invasive prenatal testing (NIPT), however, of course, other tests are still recommended before making a pregnancy decision.

Article author: Idil Gure

Article editors: Sherilyn Wen, Valerie Shirobokov