Genetic Screening 

As part of our comprehensive pre-conceptual testing, we recommend you get a blood test to see if you have a gene for certain genetic diseases.  This “carrier screening” checks for more than 300 diseases.  While most babies are born healthy, there is a small chance with each pregnancy of having a baby with a severe genetic disorder if both you and your partner carry a mutation for the same gene.

What is a carrier?

Being a carrier means that one of two copies of a gene has a change, called a mutation, that causes that copy to stop working properly. Carriers typically do not have any health problems associated with carrying a mutation and most often do not know they are carrier. However, as a carrier, there is a chance that your children could inherit the disease itself if your partner (sperm source) carries a mutation for the same disease.

Could I be a carrier?

Anyone can be a carrier of a genetic disorder, even if no one in your family is affected. The chance of being a carrier is based on your ethnic background and family history; however, some disorders are fairly common regardless of these factors.

How is carrier testing done?

Carrier testing is easy to do.  A tube of your blood is drawn and sent to the laboratory for testing. It typically takes two weeks for your doctor to get your results. While testing can never eliminate the risk of being a carrier, it does provide the opportunity to explore reproductive options if both partners are carriers for the same disorder.

Is carrier testing right for me?

Recommended carrier testing can provide you with information if you:

  • Are planning a pregnancy
  • Have a family history of a genetic disorder
  • Are at increased risk for a specific condition based on ethnicity
  • Would like additional information about your reproductive risks

What does a negative test mean?

A negative test means that no mutation was found for the disorder screened. This significantly reduces the chance that you are a carrier of this disorder. However, no carrier screen can detect all possible mutations that could cause disease, so there is always a small chance of being a carrier, even after a negative test.

What does a positive test mean?

A positive test means that a mutation was found for the disorder screened.   Even though you are a carrier, you typically will not have any symptoms associated with the disorder.  However, your children could get the disease if your partner is a carrier for the same disease.

If you test positive, the next step is to test your reproductive partner. Most likely, they will not be a carrier of the same disorder, in which case the chance to have a child with this disorder is low. However, if both you and your partner are carriers of the same disorder, there is a 1 in 4 chance to have a child with that disorder (see diagram).

What if my partner and I are both carriers for the same genetic disorder?

There are several reproductive options available for you and your partner.

  • Continue with family planning and pregnancy without prenatal testing.  In this case, 1 in 4 children are likely to get the disease, and 1 in 2 will be carriers like you.
  • Testing while pregnant to see if fetus has the disease.  This can be done by chorionic villus sampling (CVS) at 10-12 weeks of pregnancy or amniocentesis at 15-18 weeks of pregnancy.  This approach does not prevent pregnancies with the disease, but does allow you to be informed about it early in pregnancy.
  • In vitro fertilization (IVF) and preimplantation genetic diagnosis (PGD) prior to pregnancy.  This approach allows you to test embryos first, before putting them in the uterus, so as to avoid pregnancies with the disease.
  • Egg or sperm donation.  This approach reduces the risk of an affected child by eliminating one of the carriers.  Note that specific testing for the disease should be done in the sperm or egg donor.
  • Adoption is also available to couples who wish to have a child.

What are the limitations or risks regarding genetic testing?

The genetic testing will not identify all genetic abnormalities.  It is specific for only the particular disorder that is being tested. Additionally, as with all testing, it does not provide 100% accuracy. The physical risks associated with genetic testing are typically small, especially as the tests we order require only a blood sample. In some cases, genetic tests can also reveal previously unknown information about family relationships such as non-paternity or undisclosed adoption. Some patients have concerns about financial consequences of genetic testing such as the potential for discrimination or loss of employment or insurance. In May of 2008, the Genetic Information Nondiscrimination Act was signed into federal law. This offers protection against genetic discrimination in health insurance and employment.

Which genetics tests are recommended for me?

We recommend testing via an “expanded panel” of some 300 diseases.  Some of these are common (such as cystic fibrosis, Fragile X, and Spinal Muscular Atrophy), but most are not.  However, given the ease of detecting them, and the implications of missing them on the health of your child, we believe it makes sense to test.

The Table lists the common diseases according to your ancestor’s ethnic group.  However, since most people do not have pure ethnic lines among their ancestors, there is a risk to not testing for all these diseases.

 

Ethnicity

CF

Fragile X

SMA

Sickle Cell

Alpha Thal

Beta Thal

Ashkenazi Panel

Tay-Sachs

Caucasian

 

 

 

 

 

African American

 

 

 

Ashkenazi Jewish

 

 

 

 

Asian

 

 

 

Mediterranean

 

 

Hispanic

 

 

 

 

French Canadian/Cajun

 

 

 

 

Native American

 

 

 

 

Testing recommended by the American College of Medical Genetics and American College of Obstetricians & Gynecologists

Cystic Fibrosis (CF) - This is a disorder characterized by pulmonary and gastrointestinal manifestations of varying severity. Although there is a wide spectrum of clinical expression most individuals who have CF experience substantial morbidity and reduced life expectancy. The carrier frequency is 1:29 among Caucasians, 1:46 among Hispanics, 1:62 among African-Americans, and 1:90 among Asian-Americans.

Spinal Muscular Atrophy (SMA) - This is a group of inherited diseases that cause progressive muscle degeneration and weakness, eventually leading to death. One in fifty people carry this gene.

Fragile X Syndrome - This is a genetic condition involving changes in part of the X chromosome. It is the most common form of inherited intellectual disability (mental retardation) in boys. Testing is recommended to those with a family history of: fragile X, undiagnosed mental retardation, developmental delay or autism. Testing is also recommended for women that have been diagnosed with ovarian insufficiency, and some groups recommend universal testing.

Ashkenazi Jewish Panel -This is a panel including multiple disorders such as Canavan disease, Gaucher disease, Tay-sachs, Fanconi anemia, etc. These disorders are most prevalent in individuals of Ashkenazi Jewish descent.

Alpha or Beta Thalassemia - This is a broad group of disorders involving abnormalities of hemoglobin, the oxygen carrying protein of the red blood cells. This testing is recommended for individuals of African American, Asian, Mediterranean, Middle Eastern and/ or Hispanic descent.

Sickle Cell Disease - This refers to a group of disorders involving abnormal hemoglobin. It occurs most commonly in people of African origin. Approximately 1:12 African Americans have sickle cell trait. This testing includes a hemoglobin electrophoresis.

Which company do you use for your genetic testing and why?

We use Good Start Genetics for our patient's genetic testing.  Good Start Genetics is a company specializing in carrier testing. Good Start Genetics uses a powerful technology called next-generation sequencing. By using this advanced technology, it detects more mutations than other routine carrier screens. This means a higher detection rate and more confidence in your carrier test results.

What if I still have questions?

Good Start Genetics offers professional complimentary genetic counseling. To make an appointment with a licensed genetic counselor at Good Start Genetics, call 855-765-0845 or email: solutions@gsgentics.com or visit their website www.goodstartgenetics.com.

 

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