Prenatal DNA testing: which option is best for you?
According to the Center for Disease Control and Prevention (CDC), 1 in 33 babies is born with a birth defect. Prenatal DNA tests diagnose numerous genetic and neurological disorders during the first and second trimesters and allow soon-to-be parents to think about their options.
Mainly, your physician may suggest prenatal DNA testing if:
- At the time of birth, you will be 35 years of age or older
- There is a history of genetic disorders in your family
- You have had a previous child with a birth defect
- Other reasons that may be indicated by your physician
The results of a prenatal DNA test can prove useful if your child will need immediate care in which can you can organize any needs in the hospital where the delivery will take place beforehand, or get a head start on preparing anything you may need for your home in order to care for your child. Before deciding on having a test administered, discuss the details, risks, and any questions or concerns you may have with your doctor.
Cell Free DNA testing
Gestation Period: As early as Week 10
What it will detect: Down syndrome, Edwards syndrome, and Patau syndrome.
How it Works: This is a highly accurate, non-invasive prenatal DNA test that uses a blood sample from the mother. Your physician will receive the results in approximately 5 days once the sample is received in the lab.
Possible Risks: This is a non-invasive test, which results in zero risk for you or your baby.
Chorionic villus sampling (CVS)
Gestation period: Between weeks 10 – 12
What it will detect: Down’s syndrome, cystic fibrosis, Tay-Sachs,
How it works: During the procedure, a sample of cells from the placenta, called chorionic villi, is collected by guiding and inserting a needle either through the abdomen or through the cervix with the aid of ultrasonography. The test will last about 10 minutes, and your physician will receive the results in about 2-3 weeks.
Possible Risks: Spotting, infection, Rh sensitization (if the mother has Rh-negative blood and the baby has Rh-positive blood) may occur if some of the baby’s blood enters the mother’s bloodstream, this will then need to be treated. The chance of a miscarriage is about 1-2%.
Amniocentesis or Amniotic Fluid Test (AFT)
Gestation period: Between weeks 15 – 20
What it will detect: Down syndrome, Edwards syndrome, Patau syndrome, and neural tube defects that affect the spine or brain, such as spina bifida and anencephaly.
How it Works: A small amount of amniotic fluid is removed from the uterus via the abdomen using a needle. Amniotic fluid contains cells that have been shed by the fetus, which physicians use in completing the analysis. The time it takes to actually retrieve the fluid will take about 1 minute, and your physician will receive the results in about 2 weeks.
Amniocentesis performed at or after the 15 week of gestation carry a 0.33% – 0.2% chance of a miscarriage. Other possible risks include Rh sensitization, infection and slight leaking of amniotic fluid – this normally stops within one week of the procedure.
Cordocentesis or Percutaneous Umbilical Cord Blood Sampling (PUBS)
Gestation Period: After week 17
What it will detect: This method is now commonly used to detect anemia in the fetus. The procedure also allows physicians to perform a blood transfusion to the fetus if necessary.
How it works: Cordocentesis is offered if neither amniocentesis, CVS or other methods are unlikely to produce diagnostic results. A sample of blood from the fetal umbilical cord is collected by inserting a needle through the abdomen, using the guidance of ultrasonography. Test results will typically be given to your physician in a few days.
Possible Risks: Fetal bleeding, cord hematoma, decrease in the baby’s heart rate, and infection. The possibility of a miscarriage is higher with this procedure, about 1.4% -1.9%, which explains its decrease in use.
Because of the risks associated with certain tests, these are typically only offered when a carrying mother meets certain clinical indications for screening. Your doctor will present the test options that are specific to you and your pregnancy.