Carrier screening looks for possible genetic conditions that people can be carriers for. Most people do not know if they are a carrier of a disease without this screening. Typically, if both the pregnant patient and their partner are carriers of the same genetic condition, there is a risk that their child could be affected by the condition.
Most carrier screening is for recessive disorders, which means both biological parents must have disease-causing changes in the same gene for their child to be affected. Recessive disorders are conditions where both copies of the same gene need to be altered to cause the disease. The parents are unaffected because they only have one copy of the altered gene. The screening can be done before or during pregnancy using a blood sample, saliva, or cheek swab. It can help the patient learn more about risks and make informed decisions.
Carrier Screening Fact Sheet for Providers
This resource was created by the Washington State Department of Health's Prenatal Genetics Task Force to equip non-genetic providers with a clinical workflow when ordering both types of carrier screening panels –targeted screening panels and expanded screening panels.
Guidance from the WA Prenatal Genetics Task Force
The Washington State Department of Health convened a Prenatal Genetics Task Force in 2023 to provide guidance to non-genetic providers ordering prenatal genetic tests in their clinic.
The Genetics Task Force acknowledges that carrier screening is a rapidly evolving field with potential to benefit preconception and prenatal patients. It can also exacerbate existing inequities in the precision medicine and public health domains on account of different insurance coverages, geographic location, and other variable access issues.
The recently updated WA rule (WAC 246-680-020) on prenatal testing includes 14 carrier screening conditions in its standard of medical necessity for insurers. Even with the updated rule, there are still challenges present. Such as standardizing or recommending a panel or a group of panels in this current landscape (e.g., payer concerns over medical necessity and affordability).
The Task Force recommends offering carrier screening to patients but cannot specify any particular panel as the recommended option at this time. The WA Prenatal Genetics Task Force will revisit this approach on an ongoing basis.
Current Carrier Screening Guidelines
As recommended by the American College of Obstetricians and Gynecologists (ACOG), American College of Medical Genetics and Genomics (ACMG), National Society of Genetic Counselors (NSGC), Society for Maternal-Fetal Medicine (SMFM), and American Academy of Family Physicians (AAFP).
| Prenatal Test Type | ACOG | ACMG | NSGC | SMFM | AAFP |
|---|---|---|---|---|---|
| Combined Guidelines | Co-published with ACOG - same recommendations as ACOG | ||||
| Carrier Screening | (2017) Recommends offering family-history and ethnicity based carrier screening to all pregnant patients. Recommends offering pan-ethnic carrier screening if patient requests a specific condition and test is readily available | (2021) All pregnant patients and those planning a pregnancy should be offered Tier 3 carrier screening (a panel of 113 genes screening for autosomal recessive and x-linked conditions). Recommends replacing term carrier screening to expanded carrier screening, and recommends screening paradigms be more ethnicity neutral to be more inclusive of diverse populations | (2023) Recommends expanded carrier screening as an alternative to ethnicity-based carrier screening, and recommends screening be offered to all who are pregnant, considering pregnancy, or contributing biologically to pregnancy | (2017) Recommends offering family-history and ethnicity based carrier screening to all pregnant patients. Recommends offering pan-ethnic carrier screening if patient requests a specific condition and test is readily available |
(2017) Recommends offering carrier screening for cystic fibrosis, spinal muscular atrophy, fragility X syndrome, and hemoglobinopathies such as sickle cell disease to all women considering pregnancy or already pregnant. Recommends additional targeted screening based on family history and ancestry should be considered, such as screening for Tay-Sachs disease, Canavan disease, familial dysautonomia, etc. |
Resources
- DOH Resources
- Other Resources
Autosomal Dominant Inheritance
Autosomal dominant inheritance means that a condition is caused by one copy of a gene variant.
If a biological parent has an autosomal dominant condition, each of their children has a 1-in-2 chance of inheriting the variant and being affected by the condition as well.
Autosomal Recessive Inheritance
Autosomal recessive inheritance means that a condition is caused by two copies of a gene variant.
A person with 1 copy of a gene variant is called a carrier and is not affected by the condition.
If 2 biological parents are carriers of the same condition, each of their children has a 1-in-4 chance of inheriting 2 copies of the variant and being affected by the condition.
X-Linked Inheritance
X-linked inheritance means that a condition is caused by a variant located on the X chromosome.
A person who has an X-linked variant and only 1 copy of the X chromosome (XY, often assigned male at birth) is affected by the condition.
A person who has an X-linked variant and 2 copies of the X chromosome (XX, often assigned female at birth) is considered a carrier of the condition and may or may not show signs of being affected.
A carrier has a 1-in-4 chance of having a child who is also a carrier and a 1-in-4 chance of having a child who is affected by the condition.