Genetic prenatal testing refers to undergoing a medical procedure that examines an unborn baby’s deoxyribonucleic acid (DNA) for any genetic abnormalities which might cause a birth defect or an inherited disorder. Though different procedures might detect different disorders, some disorders that genetic prenatal testing screen for include Down syndrome and spina bifida. Two types of genetic prenatal testing procedures are amniocentesis and chorionic villus sampling (CVS).
Amniocentesis is safest to perform approximately between the 15th and 20th weeks of pregnancy. The doctor uses a needle to collect a sample of the amniotic fluid surrounding the unborn baby and tests the cells found in this fluid for any abnormalities. There are some risks involved with amniocentesis, such as a small chance of miscarriage.
CVS is done earlier than amniocentesis, approximately between the 10th and 13th weeks of pregnancy. For this procedure, the doctor collects a sample of the tissue from the placenta to test the cells. The doctor might employ the use of a catheter or a needle to retrieve this sample. Like amniocentesis, CVS comes with its share of risks, including a higher chance of miscarriage.
With the risks involved in undergoing genetic prenatal testing, there are many reasons why a doctor might recommend the procedure. For example, one or both parents might have a family history of inherited disorders. Or they might already have a child with an inherited disorder, like Down syndrome. Another reason to have the test is if the expectant mother is 35 years or older; this is because at this age, a pregnant woman’s baby holds a greater risk of having a chromosome problem.
While a doctor might recommend genetic prenatal testing, the choice ultimately belongs to the mother. During genetic counseling, which often precedes genetic prenatal testing, the counselor helps the mother make this choice. Together, the counselor and mother might discuss such topics as reasons for the procedure, as well as risks and benefits of undergoing the procedure. In addition, they might discuss options that a mother has if the test does show positive results for a genetic abnormality.
It is important to know that although genetic prenatal testing potentially detects abnormalities, positive results do not necessarily guarantee that an unborn baby will have a particular disorder. Instead, it might mean the baby holds a greater risk of developing the disorder. The opposite is just as true: negative results do not guarantee that an unborn baby will not develop or have an inherited disorder.