Genetic Carrier Screening Before Pregnancy

What does the evidence say about genetic carrier screening during pregnancy?

1. Carrier screening looks for gene changes linked to conditions like cystic fibrosis, Fragile X syndrome, or sickle cell disease, using a simple blood or saliva sample, and a provider may refer you to a genetic counselor to help you understand your personal risk of passing on a genetic disorder. 1
2. Carrier rates for some conditions are surprisingly common: about 1 in 25 people carry a gene change linked to cystic fibrosis and about 1 in 45 carry one linked to spinal muscular atrophy, and overall roughly 1 to 2% of all couples are at risk of having a child affected by a condition they both carry. 2
3. When both partners in a couple carry a mutation in the same gene, their reproductive options include prenatal or preimplantation genetic testing, using donor eggs or sperm, adoption, or choosing not to have biological children, decisions best made with a genetic counselor rather than from the test result alone. 2
4. Identifying carrier status before conception, rather than after a pregnancy has already started, gives couples the most reproductive choices, including options like preimplantation genetic testing during fertility care that are not available once a pregnancy is already underway. 3
5. Because self-reported ethnicity is an unreliable way to predict who carries a given gene change, current guidance favors offering the same broad, pan-ethnic screening panel to everyone rather than choosing which conditions to test for based on a person's reported ancestry. 4

Is genetic carrier screening safe in each trimester?

• First trimester. If conception is still months away, this is the ideal time for carrier screening: results come back over one to a few weeks, and having them in hand before you conceive leaves the most time and the most reproductive options if you and your partner turn out to carry the same condition.
• Second trimester. If you're already trying and haven't been screened, it's still worth asking your provider now. Screening doesn't need to delay trying to conceive, but knowing your results sooner rather than later gives you more time to make an informed decision if needed.
• Third trimester. If you conceive before getting screened, carrier screening can still be done during pregnancy, though the range of options if both partners are carriers narrows compared with knowing beforehand, since some paths to parenthood are no longer on the table once you're already pregnant.