What Every Expecting Parent Should Know About Genetic Testing

So you’re pregnant…time to celebrate!  But how to celebrate when you’re told your pregnancy could be affected by countless disorders, with names you can't even pronounce?

Thankfully, most babies are born healthy.  There are, however, a number of reasons you may want to speak with a genetic counselor (a medical professional trained in assessing the risk for birth defects and genetic disorders) before or during your pregnancy.  Some more common reasons include:

* Maternal age
* A family history of a condition
* Ethnic-based carrier testing

Maternal Age
As women age their eggs age and, consequently, so does their risk of having a child with a chromosomal abnormality.  Down syndrome (also known as Trisomy 21) is the most common chromosomal abnormality and people with Down syndrome have varying degrees of mental retardation and physical birth defects.  A woman’s estimated risk of having a child with Down syndrome is:

* At age 25, 1 in 1,250
* At age 30, 1 in 952
* At age 35, 1 in 385
* At age 40, 1 in 106
* At 45, 1 in 30
* At 49, a 1 in 11

Nevertheless, in 2007 the American College of Obstetrics and Gynecology (ACOG) recommended that all pregnant women, regardless of age, be offered screening for Down syndrome, as well as the option of diagnostic testing.  Diagnostic testing can tell with greater than 99% accuracy whether or not a pregnancy is affected with Down syndrome, Trisomy 18 and other chromosomal abnormalities, as well as certain genetic diseases (if indicated).

For more information on screening and diagnostic testing options during pregnancy, visit:
http://www.AccessDNA.com/condition/Genetic_Testing_in_Pregnancy/668

History of Genetic Disorder (or Conditions Associated with a Genetic Disorder)
Family history is one of the most important tools in assessing the risk for a birth defect and/or genetic disorder.  The risks of having an affected child is condition specific, but may depend on multiple factors such as the inheritance pattern of the disorder, the degree of the relationship of affected family members (i.e., first degree, second degree, etc.) and the gender and number of affected relatives.  

A family history of any of the following conditions (and many more not listed) may warrant seeing a genetic counselor:

* Chromosomal abnormalities (such as Down syndrome, Trisomy 13, etc.
* Muscular dystrophy
* Neurofibromatosis
* Seizures
* Recurrent miscarriages (two or more)
* Fertility problems
* Ashkenazi Jewish disorders (such as Tay-Sachs disease, Canavan disease, etc.)
* Hemophilia and other bleeding disorders
* Cystic fibrosis
* Huntington’s disease
* Mental retardation
* Autism
* Birth defects (such as spina bifida, congenital heart defects, etc.)

To find detailed information on a specific genetic condition, visit: http://www.AccessDNA.com/Genetic_Education_and_Information

Ethnic-Based Carrier Testing
Some genetic disorders, such as sickle cell disease, Tay-Sachs disease, thalassemia and cystic fibrosis, occur more frequently in people of certain ethnic backgrounds. Many of these conditions are inherited in an autosomal recessive pattern, which means two copies of a mutated gene, one from each parent, are necessary to cause the disorder. People with only one copy of a mutated gene are known as carriers. In most autosomal recessive conditions, carriers do not have any symptoms of the condition and, therefore, are often unaware that they are a carrier.

In the absence of a known family history of such disorders, the risk of being a carrier is based on a person’s ethnic background.  The risk of having a child with such disorders is based on the inheritance pattern, as well as both of the parent’s ethnic backgrounds.  As such, couples who are of the same ethnic background may have a higher risk of having a child with autosomal recessive disorders than couples who are of different ethnic backgrounds.  Couples who are related to each other by blood, such as cousins, may have an even higher risk.

Carrier testing is currently available for many autosomal recessive conditions if indicated by ethnic background.  Testing is typically performed on a blood sample, but in some cases, can be performed on cheek cells obtained from a cheek swab or saliva sample.

For more information on patterns of genetic inheritance, visit: http://www.AccessDNA.com/condition/Patterns_of_Inheritance/253

What Happens in a Genetic Counseling Session
A genetic counselor will need to know medical information about you and your family and may begin by constructing a family medical tree, called a pedigree.  This pedigree maps out the relationships between three generations of your relatives and will include information such as pregnancy information, major health conditions, known genetic disorders, age of disease diagnosis, lifestyle factors and ethnicity.

For more information on what happens in a genetic counselor session, visit:
http://www.AccessDNA.com/condition/Genetic_Consultation/392