Comment: Should women consider carrier screening before trying to conceive?

By Amber Kaplun, lead genetic counsellor for IVI RMA North America.

Are you thinking about having a baby? Here’s one thing to consider that may not yet be on your radar: preconception genetic carrier screening. This testing helps evaluate the chances of having a child with a recessive genetic condition and can offer invaluable insights for family planning.

Preconception genetic carrier screening helps evaluate the chances of having a child with a recessive genetic condition. These tests are relevant for heterosexual couples planning a family and LGBTQ+ couples using egg or sperm donors, as results guide the selection of genetically compatible donors.

Carrier screening is critical for evaluating the likelihood of a child inheriting a recessive genetic condition, which occurs when both biological parents carry a mutation in the same gene.

These conditions, such as cystic fibrosis (CF) or sickle cell anemia, can lead to significant lifelong health challenges, requiring specialised care or treatment. Understanding risks in advance allows prospective parents to make considerations for these possibilities during their family planning.

For example, consider a scenario where both partners are carriers of the CF gene. This creates a 25 per cent chance of their child being born with the condition. Armed with this knowledge, couples can explore options such as in-vitro fertilization (IVF) with preimplantation genetic testing (PGT-M) to use embryos without the condition or plan for diagnostic testing during pregnancy to prepare for the needs of a child with CF.

Expanded carrier screens typically test for over 400 conditions, making it common for individuals to be carriers of at least one condition. If one partner tests positive, testing the other partner is recommended to determine the child’s potential risk. For smaller panels of conditions, testing one partner may suffice. Ideally, this screening is completed before pregnancy.

However, carrier screening does not cover all genetic conditions. If there is a family history of genetic disorders, consulting with a physician or genetic counselor is essential to ensure appropriate testing. Additionally, while carrier screening lowers the risk, it cannot eliminate it; every pregnancy has a two to three percent chance of unexpected complications.

Starting the conversation with your provider

Patients are encouraged to work with healthcare providers—OBGYNs, genetic counselors, reproductive endocrinologists, or other professionals—for carrier screening. Direct-to-consumer tests, such as 23andMe, often lack the comprehensive results and reliability of screenings facilitated by certified labs. By working with a reproductive medicine provider, you’ll ensure the highest quality testing and expert guidance through the process.

Preparing your family history

A thorough family history is invaluable when meeting with a genetic counselor. Be ready to discuss any relatives diagnosed with genetic conditions, intellectual disabilities, autism, birth defects, or fertility issues like recurrent miscarriages. This information helps identify additional genetic tests that may be necessary beyond carrier screening.

Pros and cons of genetic carrier screening

Carrier screening offers significant benefits. When done before pregnancy, it allows medical teams to offer tests that minimize risks. Options such as testing embryos during IVF (preimplantation genetic testing) or prenatal tests like CVS (chorionic villus sampling) or amniocentesis that check for genetic abnormalities in a fetus may be available.

However, there are challenges. Insurance coverage isn’t guaranteed, though some labs provide affordable cash-pay options. Occasionally, results may reveal unexpected personal health information or leave uncertainties, such as not knowing the severity of a potential condition. Working with a genetic counselor ensures you receive the most accurate and up-to-date information.

Navigating test results

After receiving carrier screening results, here’s how common scenarios might unfold:

1. One partner is a carrier, but the other is not: The risk of having an affected child is low. In most cases, no reproductive testing is needed, as the biggest risk is having a child who is also a carrier, which is common and generally harmless.
2. Both partners are carriers of the same condition: There is a 25 percent chance of having an affected child. Couples are counseled on reproductive options, such as IVF with genetic testing of embryos (PGT-M) to avoid passing on the condition. For pregnancies already underway, diagnostic tests like CVS or amniocentesis can determine if the fetus is affected.
3. Female carrier of an X-linked condition: Women who carry X-linked conditions, such as hemophilia, have a 25 percent chance of having an affected son. Reproductive testing and counseling options are available to address these risks.
4. Neither partner is a carrier: While this outcome is rare, it’s reassuring. However, it’s important to remember that rare or mild conditions not included in the screening may still be present.

Words of wisdom for hopeful parents

Parents should expect to be a carrier of at least one condition—some people may carry several. Testing both partners simultaneously can reduce anxiety. If your results indicate high-risk findings, consult a genetic counselor for guidance. Most importantly, remember that for most couples, carrier screening provides reassurance. If challenges arise, they represent a reshaping of your family-building journey, not an end to it. Finding the right fertility care team ensures you’ll have the support you need every step of the way.