Genetic Screening: Down Syndrome and More

Soon after the pregnancy stick is positive, it’s not unusual for expecting parents to begin dreaming about their baby and imagining what the child will be like as a newborn and beyond. Whether they’re focused on the baby’s gender, features, interests, or some other quality, parents may start to paint a picture of the growing fetus and his or her future – perhaps the baby will have dark hair and blue eyes, or be a musician like dad or an athlete like mom? Although there are endless variations of what people might envision when thinking about their soon-to-be-born baby, one thing is certain – most are visualizing a healthy child.

Thinking about the baby’s risk of having a genetic anomaly is not an easy thing to do. The idea is anxiety producing and forces us to think, “What if?” The answer to that question depends on the individual, and can be complex. Genetic screening for disorders such as Down Syndrome is a choice, and how to follow up with the results of such testing is a very personal decision. The decision making begins with the expecting mom getting in touch with her own beliefs, and then having conversations with her partner, provider, and perhaps even friends that have experienced pregnancy. Genetic counseling can also help expecting couples assess their risk, based on age and family history, and then determine whether or not they’d like to be tested.

Let’s explore the different types of genetic screening

Diagnostic Tests
There are two categories of testing: diagnostic tests and screening tests. Diagnostic tests provide a definitive result regarding particular genetic disorders; however, they are invasive procedures that carry a small risk of miscarriage. The most common diagnostic test is amniocentesis. The test is performed at 16 – 20 weeks and involves the insertion of a needle into the mother’s abdomen and through the uterus to withdraw amniotic fluid that is sent to a lab. Chorionic villus sampling is another diagnostic test. The procedure is scheduled for 10 – 12 weeks and performed by retrieving a small sample of chorionic villi from the placenta for analysis.

Screening Tests
The genetic screening tests available today are better than ever and continue to evolve. Screening tests help determine the risk of a baby having a genetic disorder, as opposed to offering a definitive result, but they are non-invasive and do not carry any risk of causing a miscarriage. When a screening test shows a high risk for a given genetic disorder, the expecting mom will be offered a diagnostic test for confirmation, as all screening tests carry at least a small rate of false positives. If the screening shows a low risk for an anomaly, many women choose to skip any further testing. Below is a description of the various screening options:

  • Non-Invasive Prenatal Testing (10 – 14 weeks)
    This newest genetic screening test, currently not available to all expecting women, involves analyzing cell-free DNA from the baby that circulates in the maternal blood stream. Check with your genetic counselor, as this test may become more available soon.
  • First Trimester Screening (10 – 14 weeks)
    Blood test results, in relation to the mother’s age and the baby’s gestational age, are used to determine risk level for certain chromosomal abnormalities. An ultrasound measurement of nuchal translucency (thickness of the back of the fetal neck) can be added on for more refined results.
  • Quad Screen (15 – 20 weeks)
    A blood test that measures four markers in the mom’s blood. This screen can also test for neural tube defects such as spina bifida.
  • Fully Integrated Screening
    This screening combines the results of first trimester screening and the quad screen.
  • Fetal Anatomy Scan (18 – 20 weeks)
    An ultrasound to check the baby’s vital organs and rule out structural defects.

In most cases, prenatal genetic screening confirms that the baby is healthy; however, occasionally a genetic abnormality is identified in which case getting guidance is imperative. In addition to one’s partner, a therapist, close friend, provider, support group, or clergy can offer much needed support as one absorbs the news and reviews her options.

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