Expanded Carrier Screening & Frequently Asked Questions

By Valerie Piet · Mar 2019

Several leading genetic testing companies have unveiled expanded carrier screening offerings. What are expanded carrier screening tests, and what do they mean for physicians, genetic counselors, and expectant parents?

What Is Carrier Screening?

Carrier screening identifies carriers of gene mutations for certain genetic disorders — especially relevant before or during pregnancy. A carrier typically has no symptoms. If both parents carry a mutation in the same gene, each pregnancy has a 25% chance of the child inheriting both mutations and being affected. Carrier screening results don't change over time and don't need to be repeated for future pregnancies.

Targeted vs. Expanded Carrier Screening

Current ACOG guidelines recommend carrier screening for Cystic Fibrosis and Spinal Muscular Atrophy for all women considering pregnancy, with additional testing based on ethnicity and family history. Targeted carrier screening focuses on variants specific to an individual's background. Expanded carrier screening tests many genes — sometimes 200 or more — regardless of ethnicity. This "pan-ethnic" approach can appeal to those with gaps in family history, but comes with trade-offs: anxiety from carrier results before partners are tested, detection of conditions with variable severity, and limited consistency between panels from different companies.

Does Expanded Screening Provide Peace of Mind?

True peace of mind is hard to achieve. All expanded carrier screening panels cover only a subset of recessively inherited disorders, with little consistency between companies. A negative result doesn't modify background risk of birth defects (about 3% for all babies born in the US) or risk for chromosomal aneuploidy. A genetic counselor can help you decide which approach to carrier screening best aligns with your goals and values.