Understanding Prenatal Genetic Testing
Prenatal genetic testing will be discussed and offered at your first prenatal visit. Genetic testing gives parents information about whether or not their fetus may have certain genetic abnormalities that may impact the health and development of the fetus.
Genetic disorders are caused by changes in a person’s genes or chromosomes: Some genes may be passed on from parents to children; other genetic abnormalities result from chromosomal abnormalities that occur at conception. Understanding these conditions early on allows parents and healthcare providers to prepare for potential medical interventions or make informed decisions about the pregnancy.
There are two types of genetic testing: Prenatal screening tests and Prenatal diagnostic tests.
Prenatal screening tests
These tests can tell you the chances that your fetus has an aneuploidy (a condition in which there are missing or extra chromosomes) and a few other inherited disorders.
Screening Options:
Cell-free DNA testing: This test can be done after nine weeks and is used to analyze fetal chromosomal material in the mother’s bloodstream. It involves a blood test from the mother. There are several of these tests available on the market, but we routinely use the MaterniT® 21 PLUS test. It screens for certain chromosomal abnormalities that could affect your baby’s health and development—such as trisomy 21 (Down syndrome) and sex chromosome aneuploidies (SCAs, or abnormal numbers of X or Y chromosomes)—and can also detect your baby’s gender. The cost of these tests will be covered by insurance companies at different rates, so we recommend checking with your insurance company before ordering.
First-trimester screening with Nuchal Translucency: This test combines an ultrasound at approximately 12 weeks gestation with blood work. It analyzes a woman's risk for Down syndrome (trisomy 21), as well as trisomy 13 and 18.
Prenatal diagnostic tests
These tests can tell you whether your fetus actually has certain disorders. These tests are done on cells from the fetus or placenta obtained through amniocentesis or chorionic villis sampling (CVS). Learn more here: Prenatal Genetic Diagnostic Tests.
Diagnostic Test:
Chorionic Villus Sampling or Amniocentesis: These are invasive tests that entail sampling the placenta or amniotic fluid with a needle. We are doing these tests less frequently now, as we have access to better non-invasive tests listed above that pose no risk to the fetus.
If you would like genetic counseling prior to becoming pregnant, please contact our office. Carrier screening is a type of genetic test that can tell you whether you carry a gene for certain genetic disorders. If you have carrier screening before you get pregnant, you have several options, including exploring IVF, which allows the embryo to be tested before it is transferred to the uterus.
If you have carrier screening after you get pregnant, your options are more limited. In either case, your ob-gyn or a genetic counselor can explain the risks of having a child with the disorder.
What Expectant Parents Should Consider
Understanding Risks and Benefits: Each test comes with its own set of risks and benefits. It's important to discuss these factors with your healthcare provider to make an informed decision that aligns with your preferences and medical history.
Timing of Testing: Some tests, such as first-trimester screenings, are conducted early in pregnancy, while others, like amniocentesis, are performed later. Your healthcare provider will recommend the most appropriate timing based on your individual circumstances.
Emotional Preparedness: It's crucial to consider the emotional impact of these tests. Understanding that results, whether positive or negative, may impact decision-making about the pregnancy can be emotionally challenging. Seek support from your healthcare provider or a genetic counselor if needed.
Continued Care: Regardless of test results, continued prenatal care is essential for monitoring the baby's health and the mother's well-being throughout the pregnancy.
It is your choice whether to have prenatal testing. Your personal beliefs and values are important factors in the decision about prenatal testing.
It can be helpful to think about how you would use the results of prenatal screening tests in your pregnancy care. Remember that a positive screening test tells you only that you are at higher risk of having a baby with Down syndrome or another aneuploidy. A diagnostic test should be done if you want to know a more certain result. Some parents want to know beforehand that their baby will be born with a genetic disorder. This knowledge gives parents time to learn about the disorder and plan for the medical care that the child may need. Some parents may decide to end the pregnancy in certain situations.
Other parents do not want to know this information before the child is born. In this case, you may decide not to have follow-up diagnostic testing if a screening test result is positive. Or you may decide not to have any testing at all. There is no right or wrong answer.
