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. The
screening checks for more than 175 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 of a genetic condition means that one of two copies of
a gene has mutated and does not work correctly. 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
(or 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 (or sperm source) is a carrier for the same disease.
If you test positive, the next step is to test your reproductive partner.
If your partner is not a carrier, 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.
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.
Undergo 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.
Through an egg or sperm donation, you can choose a donor who does not carry
the mutation, eliminating much of the risks. 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 over 170 diseases.
Some of these are common (such as cystic fibrosis, Fragile X, and Spinal
Muscular Atrophy), but most are not. Because these tests are easy to perform,
we highly recommend testing for all conditions, even the rare ones, just
to be safe.
This table lists the common diseases according to ethnicity. Most people
have some mixed ethnicities somewhere in their family history, meaning
it is a good idea to test for all conditions, even if you do not think
you would be at risk.
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 learning disorders, developmental delays, or
autism. Testing is also recommended for women that have been diagnosed
with ovarian insufficiency.
Ashkenazi Jewish Panel -This is a panel that tests for 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.
Which Company Do You Use for Your Genetic Testing and Why?
We use Counsyl for our patient's genetic testing. Counsyl is a company
specializing in DNA testing. Counsyl uses a powerful technology called
next-generation sequencing. This state-of-the-art technology 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?
Counsyl offers professional complimentary genetic counseling. To request
an appointment with a licensed genetic counselor at Counsyl, call 888-COUNSYL (888.268.6795) or visit their website
www.counsyl.com.
