Prenatal genetic screening gives pregnant women information on whether their fetus has certain genetic disorders. Genetic disorders are caused by changes in a person’s genes or chromosomes.
Types of Prenatal Screening Tests
Screening tests can tell you your risk of having a baby with certain disorders. Carrier screening is done on parents (or those just thinking about becoming parents) using a blood sample or tissue sample swabbed from inside the cheek. These tests are used to find out whether a person carries a gene for certain inherited disorders. Carrier screening can be done before or during pregnancy.
Prenatal genetic screening tests of the pregnant woman’s blood and findings from ultrasound exams can screen the fetus for aneuploidy; defects of the brain and spine called neural tube defects (NTDs); and some defects of the abdomen, heart, and facial features. This FAQ focuses on these tests. They include first-trimester screening, second-trimester screening, combined first- and second-trimester screening, and cell-free DNA testing.
First Trimester Screening
First-trimester screening includes a test of the pregnant woman’s blood and an ultrasound exam. Both tests usually are done together between 10 weeks and 13 weeks of pregnancy:
- The blood test measures the level of two substances.
- The ultrasound exam, called a nuchal translucency screening, measures the thickness of space at the back of the fetus’s neck. An abnormal measurement means there is an increased risk that the fetus has Down syndrome (trisomy 21) or another type of aneuploidy. It also is linked to physical defects of the heart, abdominal wall, and skeleton.
Cell-Free DNA Testing
Cell-free DNA is the small amount of DNA that is released from the placenta into a pregnant woman’s bloodstream. The cell-free DNA in a sample of a woman’s blood can be screened for Down syndrome, Patau syndrome (trisomy 13), Edwards syndrome, and problems with the number of sex chromosomes.
This test can be done starting at 10 weeks of pregnancy. It takes about 1 week to get the results. A positive cell-free DNA test result should be followed by a diagnostic test with amniocentesis or CVS.
Make an Appointment at Raleigh OB/GYN Centre
The physicians, nurses, and medical staff at Raleigh OB/GYN offer a comprehensive list of gynecological and obstetric services to the women of the Raleigh, NC area. If you have questions or concerns about prenatal care, including genetic screening, call our office at (919) 876-8225 to make an appointment.
