What is Ethnicity-Based Carrier Screening?

April 10, 2017


A person can be a carrier for a genetic disorder without showing any outward symptoms of that disorder. Although the chance is unlikely, if their partner happens to also be a carrier for the same disorder, the risk of having a child with the disorder is greatly increased. There are certain genetic disorders that are more common in specific ethnic groups. However, keep in mind, anyone can be a carrier for any genetic disorder regardless of ethnicity.

If both parents are carriers for the same genetic disorder, then their pregnancy would have a 25% (1 in 4) chance to be affected by that disorder. This means there is a 75% (3 in 4) chance that the baby will not be affected. The first step is to complete a blood (or saliva) test on both parents to determine their carrier status. If blood tests determine that both parents are carriers of the same genetic disorder, prenatal diagnostic testing can be done to diagnose the disease during pregnancy. These tests include chorionic villus sampling (CVS) and amniocentesis.

It is recommended that individuals with Eastern European Jewish heritage be screened for certain genetic disorders. People of this heritage are at a high risk of being carriers for disorders such as Tay-Sachs disease, canavan disease, familial dysautonomia, and cystic fibrosis. Read more about the disorders more common with Ashkenazi Jewish ancestry here.

Caucasians are at an increased risk for being a carrier for cystic fibrosis. Cystic fibrosis is a disease which causes thick mucus to build up in the lungs, leading to gradual damage of the respiratory system and chronic digestive problems.  Some symptoms include frequent lung infections, coughing, or wheezing, fat malabsorption, poor growth, fatigue, complicated pregnancies in females, and infertility in males. The combined complications lead to a shortened life expectancy. For caucasians, there is a 1 in 25 chance to be a carrier for this disorder.

Individuals of Asian ethnicity are at an increased risk for a disorder called alpha thalassemia. Alpha thalassemia is a blood disorder that reduces the production of hemoglobin. Hemoglobin is the protein in red blood cells that carries oxygen to cells throughout the body. Two main types of alpha thalassemia can cause health problems. These disorders range from mild to severe. Mild cases, such as “HbH disease” can lead to an overgrowth of the upper jaw and an unusually prominent forehead. Severe cases, such as “Hb Bart Syndrome” can lead to stillbirth. For Asians, there is a 1 in 20 chance to be a carrier for this disorder.

African Americans are at an increased risk to be a carrier for sickle cell anemia, which people refer to as sickle cell trait. People with sickle cell anemia have abnormally shaped (sickled) blood cells which can cause pain and other symptoms. When red blood cells sickle, they break down prematurely, which can lead to anemia. Anemia can cause shortness of breath, fatigue, and delayed growth and development in children. The rapid breakdown of red blood cells may also cause yellowing of the eyes and skin, which are signs of jaundice. A more severe complication of sickle cell disease is high blood pressure in the blood vessels that supply the lungs (pulmonary hypertension). Pulmonary hypertension occurs in about one-third of adults with sickle cell disease and can lead to heart failure. There is a 1 in 10 chance to be a carrier for this disorder when you have African American ancestry.

Completing ethnicity-based carrier testing, either before or during pregnancy, will help partners make informed decisions about the health of their future or current pregnancy. Universal carrier screening is also an option, giving you the opportunity to complete carrier screening for a variety of disorders, including disorders more common in your ethnic group. A prenatal genetic counselor can help discuss the benefits and limitations of carrier screening and guide you in selecting the best test for you.