Understanding carrier screening for family planning

When planning a family, you and your partner may choose to have genetic testing before having children to determine if you have a risk of passing on specific genetic disorders.

Genetic testing is available to people who are pregnant or planning a pregnancy. Carrier screening has gained importance in family planning as it helps identify genetic conditions that can be passed on to children.

Based on your family history, or pedigree, a genetic counselor can advise you on:

• Genetic screening to consider, insurance coverage and cost
• What genetic testing may or may not determine
• Your potential risk of passing genetic disorders onto your children

People should consider genetic counseling and testing regardless of their family history of inherited conditions, such as cystic fibrosis, spinal muscular atrophy or muscular dystrophy. Approximately 80% of children who develop a genetic disorder have no family history of the condition.

What is carrier screening?

People receive two copies of each gene in their body: one inherited from the mother and the other from the father. Carrier screening determines if a person carries a nonworking copy of a gene associated with a specific genetic condition.

People with one working copy and one nonworking copy of a gene are referred to as a "carrier" for the condition. They typically are not affected by the condition themselves. This is because carriers have one copy of the gene that functions normally, providing them protection against the condition. Most people are carriers of at least one genetic condition, and some are carriers of more than one condition.

Autosomal recessive conditions

Autosomal recessive conditions, like cystic fibrosis, occur when a person inherits two nonworking copies of a gene, one gene from each of the parents who are carriers.

If a person is identified as a carrier, their partner, egg donor or sperm donor are offered the same testing to determine if they are carriers of the same conditions. If both partners are carriers of the same condition, there is a 25% chance that their child may inherit two nonworking copies of the gene and be affected by the condition. Approximately 2% to 3% of couples are carriers of the same condition.

Although certain genetic conditions may be individually rare, collectively, their prevalence is more significant and accounts for more than 10% of pediatric deaths.

Carrier screening for family planning

While carrier screening can be done when a person is pregnant, it's especially beneficial for preconception planning. Couples are empowered to make informed decisions about family planning, taking into account their carrier status for specific conditions. Based on the screening findings, some people may opt for alternative reproductive measures, such as in vitro fertilization, or IVF.

Carrier testing may look for a single genetic condition based on family history. Expanded carrier screening looks for genes linked to many genetic diseases that are not only based on family history or ethnic background.

Carrier screening now is more accessible and affordable than ever before. Couples discussing family planning can ask their care team for a referral to genetic counseling. Self-referral for the service also is available. Genetic counseling appointments can be conducted virtually with genetic testing performed through a blood draw or a saliva test.

After genetic testing, the genetic counselor explains the results and risks are identified. The information is shared with the patient's primary care provider or OB-GYN.

Carrier screening is a valuable tool in family planning, offering couples vital information about their carrier status for up to 500 genetic conditions. It can help people make informed decisions about reproductive options, allows for early intervention and treatment, if necessary, and informs the risk of passing on genetic conditions to their children.

Rebecca Jirik specializes in genetics or inherited diseases.