Prenatal Testing: What Is Genetic Carrier Screening?

Prenatal Testing: What Is Genetic Carrier Screening?

Is Genetic Carrier Screening Necessary?

For many pregnant women, tests at prenatal visits are pretty routine. Often, these tests center around blood draws to check for signs such as a nutritional imbalance. And, of course, the first blood test is to confirm that pregnancy has happened. But as the pregnancy progresses, tests are often targeted to check for issues that can impact not just the pregnancy but the health of mom and baby. In particular, many women are encouraged to undergo genetic carrier screening. But when these screenings occur can vary depending on how the pregnancy began.

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Genetic carrier screening explained

Genetic carrier screening is precise as the procedure sounds. Usually, the process is a non-invasive or minimally invasive exam that checks for potential congenital. The test is applied to egg and sperm donors, performed on couples undergoing infertility treatment, and can be given to couples to conceive naturally. In particular, practitioners are trying to determine if a patient carries recessive genetic disorders that could impact health of a baby. While the focus is commonly on chromosomal disorders such as Down's syndrome, other health conditions like Tay Sachs disease are also of concern.

Which people should get genetic carrier screening

Technically, any individual can request genetic carrier screening. However, practitioners usually follow specific guidelines based on an individual's age, ethnicity, or pre-existing conditions to recommend that particular people get tested. For example, older women and couples trying to conceive or a person with a family history of a recessive genetic disorder would be strong candidates for testing.

What does a positive test mean?

Testing positive for a genetic condition doesn't automatically mean that any child conceived by that individual will inherit the disease. Except for fragile X syndrome, both parents must test positive as carriers to warrant concern that a child may potentially inherit the disease.

When should testing occur

The answer of when to undergo genetic carrier screening can vary based on life stages, health history, and goals. For example, an individual with a known family history of recessive genetic diseases may opt to get tested before attempting to conceive. Meanwhile, women and couples undergoing specific fertility treatments such as in-vitro fertilization (IVF) may have embryos tested before being transferred to a woman's uterus. And for couples that conceive naturally, genetic testing can occur between 10-18 weeks around the time of the nuchal screening ultrasound.

What to remember about genetic screening

Genetic carrier screening can give insight into whether an individual or couple may have a higher risk of giving birth to a child with a genetic condition or defect. But the tests cannot predict the future. In other words, a person or couple who tests positive may go on to have healthy children naturally or through assistive reproductive treatments (ART). Even nuchal screening and blood tests cannot confidently say that a baby will be born with defects. Individuals concerned about recessive genetic disorders and the risk of passing a condition to future children should speak with a fertility specialist or genetic counselor.

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