Prenatal screening and testing for genetic abnormalities

At your first appointment, your obstetrician will probably ask if you want to consider prenatal screening or testing. The optional first trimester screening is typically done between weeks 10-13, so here are a few things to keep in mind as you make this decision:

  • It's important to know the difference between prenatal screening and testing. Screening determines the likelihood your baby could be born with a genetic disorder. Testing gives a more definitive "yes" or "no."
  • Genetic disorders are caused by abnormalities with your baby's genes or chromosomes. Sometimes there's mutation – a change in the genes. This can lead to disorders such as sickle cell anemia, cystic fibrosis and Tay-Sachs disease. A fetus could also be missing or have extra chromosomes. That can indicate conditions such as Down syndrome.
  • Prenatal screening and testing can pick up these genetic issues, but there can be others that wouldn't be identified until birth or later in an individual's lifetime.
Prenatal screening, testing can reveal possible genetic abnormalities in fetus

"There are many benefits to prenatal screening, including reassurance and the ability to make informed decisions. But the screening can also cause anxiety, especially since there's always the possibility of false positives or negatives," says Tiffany Stadnick, MD, an obstetrician and independent member of the HonorHealth medical staff. "With all that in mind, it's ultimately the parents-to-be who need to decide. I usually ask my patients to consider what, if anything, they might do differently if they had this information."

The first trimester screening is offered to all patients, regardless of risk factors. The test involves blood work correlated to an ultrasound that scans for chromosomal abnormalities. If you're age 35 or older, or have a family history of genetic disorders, you may also choose to have prenatal testing such as amniocentesis or chorionic villus sampling (CVS). As your pregnancy progresses, you'll continue to have ultrasound screenings that check for any major physical issues.

"Some people want to know ahead of time if their baby will have challenges, and others prefer not to. A lot depends on your personal beliefs and values. There really is no right or wrong answer," says Dr. Stadnick.

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