Sunday, February 14, 2016

A Helpful Form to Prepare For Preconception Genetic Testing

Genetic testing prior to conception can easily identify known genetic risks prior to conception. This is important because many of the inherited diseases which can be fatal in childhood can now be easily avoided, if you know your risks and the options for conception without passing along fatal genes.

Some of these diseases include:

Cystic Fibrosis
Cystic fibrosis is a life-threatening, genetic disease that causes persistent lung infections and progressively limits the ability to breathe. In people with CF, a defective gene causes a thick, buildup of mucus in the lungs, pancreas and other organs. In the lungs, the mucus clogs the airways and traps bacteria leading to infections, extensive lung damage and eventually, respiratory failure. In the pancreas, the mucus prevents the release of digestive enzymes that allow the body to break down food and absorb vital nutrients.

A baby with Tay-Sachs disease appears healthy at birth, and seems to be developing normally for a few months. Symptoms generally appear by six months of age. While symptoms vary from one child to the next, there is always a slowing down of development. Gradually, Tay-Sachs children lose motor skills and mental functions. Over time, the child becomes blind, deaf, mentally retarded, paralyzed and non responsive to the environment. Tay-Sachs children usually die by age five.

Children with Tay-Sachs disease lack a vital enzyme, hexosaminidase A (Hex-A). Hex-A is needed for the body to break down a fatty waste substance found in brain cells. Without Hex-A, this substance accumulates abnormally and causes progressive damage until the nervous system can no longer sustain life.

Sickle Cell Disease
Sickle cell disease is an inherited blood disorder that affects red blood cells. People with sickle cell disease have red blood cells that contain mostly hemoglobin* S, an abnormal type of hemoglobin. Sometimes these red blood cells become sickle-shaped (crescent shaped) and have difficulty passing through small blood vessels.

When sickle-shaped cells block small blood vessels, less blood can each that part of the body. Tissue that does not receive a normal blood flow eventually becomes damaged. This is what causes the complications of sickle cell disease. There is currently no universal cure for sickle cell disease.

These diseases are inherited if both parents carry the recessive gene associated with that specific disease. As a review from freshman year biology class, here is a refresher on Punnett Squares:
If both parents are carriers, they will show no symptoms of the disease. Each time they naturally conceive a child that baby will have the following risks:
  • 25% chance of being "RR," meaning they inherited both dominant copies of the gene from their parents. They will have 0% chance of passing along that trait to their future offspring. 
  • 50% chance of being "Rr," meaning they inherited one copy of the recessive trait. While these children will not develop the disease, they will have a 50% chance of passing this trait along to their offspring. 
  • 25% chance of being "rr," meaning they inherited the disease. What this means is different for each illness. Some illnesses (e.g., Tay-Sachs, Canavan Disease) are almost always fatal in infancy/toddlerhood. Others (e.g., Cystic Fibrosis) may lead to an overall shortened lifespan, but with proper treatment and management the individual often survives to early adulthood. 
The most important step you can take prior to conception is knowing your risks and possibly requesting testing prior to conception. 

Here is a form I created to help you determine which disease(s) you may be at risk for -- this form should not take the place of medical advice, but should be used as a beginning step in discussing your risk factors with your gynecologist prior to trying to conceive.

Click here to access the form

Best of luck on your journey to conceiving a healthy baby!

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