What To Expect During Genetic Prenatal Testing

By: South Florida Perinatal Medicine

If you have been referred for genetic prenatal testing your pregnancy is probably at high risk for chromosomal abnormalities or genetic defects. It is important to remember that doing a test does not mean that you won’t have a healthy baby. Genetic tests are a means to determine what your risks are so that you can get the specialized prenatal care that you require as well as prepare for the future.

Before you go for genetic prenatal testing you will typically be asked to meet with a genetic counselor who will explain your options. He/she will collect detailed information about your medical history as well as that of your family in order to fully understand your situation and provide the right advice. If your maternal age is above 35 years you may be asked to do tests even if you don’t exhibit any signs or have a family history of genetic defects.

There are many different types of tests for identifying your risks. Depending on the type of test, a sample of your blood, skin, amniotic fluid or other tissue will be collected and sent to a lab for analysis. These tests may be conducted by your doctor, a medical geneticist or nurse practitioner.

Here is a quick guide on what to expect during genetic prenatal testing.

• Blood sample: A blood sample will be obtained by inserting a needle into a vein in your arm.
• Cheek swab: In some situations, a swab sample from the inside of your cheek may be collected for genetic testing.
• Amniocentesis: This form of prenatal genetic testing relies on a sample of your amniotic fluid. Your doctor will insert a thin, hollow needle through your abdominal wall and into your uterus. A small amount of amniotic fluid is then withdrawn into a syringe, and the needle is removed.
• Ultrasound: Ultrasound high frequency sound waves are sent straight down via the transducer to view the inside of your abdomen. The returning echoes are analyzed by the computer and transmitted as moving images of the fetus.
  • Level 2 ultrasound: A detailed, full fetal anatomy scan with sophisticated imaging for detection of abnormalities
  • 3D sonogram: Provides three dimensional images of the fetus to determine if there are any fetal anomolies
  • 4D ultrasound: 3D sonograms in real time
  • Hysterosonogram: A saline infusion sonography to detect abnormalities in the uterine cavity
• Chorionic villus sampling: During this test a medical professional will take a tissue sample from the placenta. This may be done with a tube (catheter) through your cervix or through your abdominal wall and uterus using a thin needle.
• Non-Invasive Prenatal Testing (NIPT): A new option in the prenatal screening and using cell-free fetal DNA. Testing is typically done between 10-22 weeks.
• First trimester screening: A non-invasive screening option combining a maternal blood screening test with an ultrasound evaluation of the fetus.
• Integrated screening: This prenatal testing procedure combines measurements from a nuchal translucency ultrasound and two blood tests.
• Sequential Screening: Two blood tests measure proteins that are made by the developing baby and placenta. The first blood test is taken between the 11th and 13th week of your pregnancy. The second blood test is taken ideally between 15 and 18 weeks, although it can be done up to the 21st week. An ultrasound is performed between the 11th and 13th week to confirm the right timeframe for the screening. This also includes the nuchal translucency.
• Percutaneous umbilical blood sampling: The procedure is similar to amniocentesis except that it retrieves blood from the fetus rather than amniotic fluid. An advanced imaging ultrasound determines the location where the umbilical cord inserts into the placenta and guides a thin needle through the abdomen and uterine walls to the umbilical cord. The inserted needle retrieves a small sample of fetal blood from the umbilical cord.

Genetic prenatal testing is voluntary and you always have the option to say no. Knowing what you’re dealing with, however, helps make important (and informed) decisions about next steps.

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