Q -
Hi. I am a 26 year old person at risk for HD. My father has it. So I have a 50-50% chance of getting it and my children that I would like to have one day have a 25-25% chance, right? I am married and would like to start a family next year, but how do I have a child without passing on HD? I have thought about 1) getting the blood test, but I am not sure if I or my significant other can handle the results 2) doing in-vitro to get rid of the "bad DNA". What can I do? How can I have my own children without passing HD to them?
Thank you for your time.
A -
Thank you for your question. Please use the following information as a reference point and I encourage you to speak with a genetics counselor about your unique situation.
First of all, it is important to understand autosomal dominant inheritance, the method by which the HD mutation is passed through generations. If you have a parent with HD you have a 50% chance of inheriting the mutation and developing the disease. As you are aware, because your biological father is a carrier, there is a 50% chance that you are also a carrier. Because you do not know your gene status I can see why you would say there is a 25% chance that your children will get HD (50% chance for you multiplied by a 50% chance for your children equals a 25% chance). But that is a theoretical percentage. In reality there is either a 0% or 50% chance that your children will get HD, depending on whether or not you carry the mutation.
All of this does make the decision about having children difficult. It sounds like you are familiar with the options currently available for having biological children, but I will try to clarify.
In vitro fertilization with preimplantation genetic diagnosis (IVF with PGD)
I believe this is what you meant about using in vitro to get rid of the mutated DNA. The process of IVF means that both sperm and eggs are harvested from the parents and fertilization occurs outside of the mother. PGD involves testing the created embryos for the HD mutation. Only the "HD free" embryos are implanted into the mother. This method is useful for people who do not want to know their own gene status but want to be certain that they do not pass HD on to their children. The medical staff can perform both IVF and PGD without letting the couple know what the status of the embryos is. Unfortunately, this technique can be very expensive, up to $20,000 a cycle. For some couples it only takes one cycle to get pregnant, but for others it can take many.
Amniocentesis (prenatal testing of the fetus)
Another option is to create a baby in vivo (through intercourse) and have an amniocentesis performed sometime in the first trimester. This will tell you the gene status of the fetus. However, if the fetus is positive for HD, you will inadvertently know your own gene status and have to deal with the difficult decision about whether or not to terminate the pregnancy.
Genetic testing
Just to clarify, there are three types of genetic testing:
- Prenatal: done in the first trimester of a pregnancy
- Confirmatory: done when a doctor would like to confirm their clinical diagnosis of HD with a blood test
- Predictive: DNA testing of people at risk but not symptomatic. Predictive testing involves a series of visits to a genetic counselor and can cost between $300 to $1000.
The decision you are facing is a very personal one. I hope this information is helpful to you.
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