Genetic Screening Tests for Women 35 or Older
Chorionic Villus Sampling (CVS) continued...
During this test, a small sample of cells, called chorionic villi, is taken from the placenta. Chorionic villi are tiny parts of the placenta that are formed from the fertilized egg, so they have the same genes as your babies. To get the cells, a doctor passes a needle through the vagina or the abdomen, depending on the location of the placenta. The cells are used to check your babies' chromosomes, just like amniocentesis.
CVS and amniocentesis usually involve genetic counseling, where you speak with a counselor about your risk for genetic disorders. You will also learn about the risks and benefits of the procedures. Because of the risks associated with CVS with a twin pregnancy, it is not commonly done.
Noninvasive Prenatal Diagnosis
This new blood test, also called cell-free DNA testing, is used to show whether you are at risk for having babies with chromosome problems. Because it's done by using a sample of your blood, it's less invasive than amniocentesis or CVS.
The test finds a baby's DNA floating around in the mother's blood. The result determines the chance that the baby could be born with Down syndrome, trisomy 18, or trisomy 13.
Using this test in twins remains controversial. Ask your doctor or genetic counselor if this test is appropriate for you.