Genetics Northern California

Ethnicity-Based Genetic Screening


Genetic diseases can happen to anyone, but a small number of genetic diseases happen more often in specific ethnic and racial groups. The Prenatal Ethnicity-Based Genetic Screening Program at Kaiser Permanente Northern California offers optional genetic testing to prenatal patients. Genetic carrier screening is targeted to the ethnic groups that have the highest risk for these conditions..

What causes genetic diseases?
Which genetic diseases are included in ethnicity-based carrier screening?
Which screening test should I have?
How are these disease inherited? 

What does it mean to be a carrier?

How do I find out if I am a carrier?
What does a negative result mean?
What does a positive result mean?
Why have prenatal testing?
What if I don't want prenatal testing?
Can I have testing if I'm not pregnant?

What causes genetic diseases?
Genes are the basic units of inheritance that determine many characteristics of a developing baby, such as eye color, height, and blood type. Genes that do not work properly are responsible for genetic diseases. Everyone carries genes that can potentially cause genetic diseases.

Which genetic diseases are included in ethnicity-based carrier screening?

  1. Canavan disease
  2. Cystic fibrosis
  3. Familial dysautonomia
  4. Hemoglobinopathies (inherited blood diseases)
     - Hemoglobin E
     - Sickle cell diseases
     - Thalassemia diseases
  5. Tay Sachs disease  

Which screening test should I have? 
Most of the time, there is nothing in your family's medical history to tell you which diseases your baby could be at risk for. One way to identify risks is by considering where your ancestors lived before they came to the United States. Each condition is more common in people from certain parts of the world. 

  • If  you have any Southeast Asian background consider testing for hemoglobinopathies (genetic blood diseases), including hemoglobin E.

  • If either  you OR your baby's father have any African (Black) background consider testing for hemoglobinopathies (genetic blood diseases), including sickle cell disease.

  • If either  you OR your baby's father have any European (Caucasian/White) background consider testing for cystic fibrosis.

  • If both  you AND your baby's father have any Eastern European Jewish (Ashkenazi Jewish) background consider testing for Tay-Sachs disease, Canavan disease, and familial dysautonomia.

How are these disease inherited?
All of the conditions screened for by this program are inherited as autosomal recessive disorders. All of your genes come in pairs; you get one from each parent. In order to have one of the above diseases, a baby must receive two non-working genes for the same disease. That means both parents must be carriers of a specific genetic trait for the pregnancy to be at risk.

What does it mean to be a carrier?
A person with one non-working gene for any of these diseases is called a carrier. A carrier also has a working copy of that same gene. Being a carrier for any of these conditions does not affect your health. The importance of being a carrier is that your child may inherit the disease, even though you are healthy. The only time a child is at risk for one of these conditions is when both parents are carriers for the same genetic disease.

When both parents are carriers for the same genetic disease, there is a 1 in 4 (or 25%) chance that the baby will have the disease. There is also a 3 out of 4 (or 75%) chance that the baby will not have the disease.

If only one parent passes on a non-working gene to a baby, the baby will not have a disease, but will be a healthy carrier just like the parent.

How do I find out if I am a carrier?
The only way to find out if you are a carrier is to have a genetic blood test. During an early prenatal visit at Kaiser Permanente you will fill out a form about your ethnicity and your partner's ethnicity. Your answers will determine which tests you are eligible to have. If you request testing, a blood test will be ordered to identify whether or not you are a carrier.

What does a negative result mean?
A negative result means that you are most likely not a carrier for that particular disease. Therefore, no further testing is generally needed. These tests are very accurate, but they will not identify all carriers.

What does a positive result mean?
A positive result means that you are a carrier for that particular disease. Follow-up testing will be offered to the father of the baby to find out if your pregnancy is at high-risk for the condition. If your pregnancy is at high-risk, you are offered prenatal testing to determine whether or not the developing baby has the condition.

Why have prenatal testing?
There are no prenatal treatments to help lessen the symptoms of these conditions, and the disorders are not curable. For most women who have prenatal testing, the test provides reassurance that the baby does not have the genetic disease. Some people who learn that their baby has one of these diseases may use the information to decide whether or not to end their pregnancy. Others may use this information to help them prepare for taking care of a child with special medical needs. Your genetic counselor will discuss your options in detail and provide ongoing support.

What if I don't want prenatal testing?
If you choose to not have prenatal testing, the baby can be tested shortly after it is born. The California Newborn Screening Program tests for cystic fibrosis, sickle cell disease, and the thalassemia diseases, along with certain other metabolic and endocrine disorders.

Can I have testing if I'm not pregnant?
If you are planning a pregnancy, you may want to consider genetic carrier testing before you are pregnant. This is also called preconception ethnicity-based screening (i.e., screening before the pregnancy begins). Preconception screening has the advantage of giving additional reproductive options to couples found to be at risk for one of these conditions. Any woman interested in preconception screening can arrange testing through her gynecologist. The same guidelines followed by the prenatal screening program should be followed for preconception screening.

Reviewed by: Christy Wold, MS, Kimberly Barr, MS
Last reviewed: January 11, 2013