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Choosing an egg donor: Genetic carrier testing update

couple choosing an egg donorGenetic carrier testing is one of the main topics fertility patients ask about when choosing an egg donor. A lot has changed in genetic carrier testing since my last blog about it last year. Because of the advancements made in these tests, InVia has gone from testing for 13 different diseases to now test for 311 different diseases, over 2,600 mutations, and 299 genes. Because we are testing for so much, it is less and less common to find egg donors (and patients) who do not carry any of the diseases.

Our process for screening and for disclosing screening results has changed as well. We now disclose to a donor's potential egg donation recipients any disease that the donor is shown to carry—and we then test the male sperm source. If it is a male partner, we can easily draw his blood and test him in the office. If it is a sperm donor, we reach out to the sperm bank and see if they have any donors who have been tested for this specific disease. The egg donor and the intended egg donation recipients, respectively, then have consultations with a genetic counselor.

As long as the sperm source and the egg donor do not carry the same disease, we have no hesitation moving forward with the egg donation cycle. There is full disclosure to the egg donation recipients and with the advice from a genetic counselor; the egg donation recipients of course has the final say in whether choosing an egg donor.

Should You Worry If A Donor Has a Disease?

There are some important things to think about in choosing an egg donor when it comes time to review the donor's genetic carrier testing results:

These diseases are autosomal recessive, meaning both the egg donor and the sperm provider would need to have the same disease for there to be a chance of producing an affected child. Even in that case, there is only a 25% chance of having an affected child. There would be a 50% chance of having a child that is a carrier, and there would be a 25% chance of producing a child that is neither affected nor a carrier. That 25% chance may seem small, but to us, it is monumental. We would advise the egg donor recipient to select another egg donor in that case.

On the flipside of that statement, if only one contributor to the embryo (either egg donor or sperm source) is a carrier of a disease, there is a 50% chance of having a child that is a carrier of the disease and there is a 50% chance of having a child that is neither a carrier nor affected by the disease. Please see the image below:

Autosomal recessive inheritance of a genetic disease

X-Linked and Y-Linked Diseases

Some of these diseases are X-Linked, meaning they are only carried on the X chromosome. Females are XX chromosomes and males are XY chromosomes. X-Linked recessive conditions are caused by a gene alteration on the X chromosome. As males have only one X chromosome, if they have a gene alteration on their X chromosome, they will develop the condition.

Females rarely show signs of X-Linked recessive conditions as they usually have a second unaltered copy of the gene on their other X chromosome to compensate for an altered gene. A female who has a gene alteration on one of her X chromosomes is said to be a carrier for the X-Linked recessive condition.

Males transmit their Y chromosome to their sons. This means that sons will not inherit an X-Linked recessive condition from their father, and therefore, if an egg donor came back as a carrier of an X-Linked disease, we would not test the sperm source.

When the egg donor is a carrier for an X-Linked recessive condition, each daughter has a 50% chance of inheriting the gene alteration and so being a carrier for the condition. Each son has a 50% chance of inheriting the gene alteration and so inheriting the condition.

When the sperm source has an X-Linked condition, his sons will not be affected. His daughters will be a carrier for the condition.

To see a fertility specialist who provides thorough genetic screening to all prospective donors, make an appointment at one of InVia's four Chicago area fertility clinics.

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Egg donation InVia Fertility Specialists

Vicki Meagher

Vicki Meagher

Vicki Meagher has worked with InVia Fertility Specialists since 2006. She is our Third Party Coordinator, so she works with our patients that need an egg donor, sperm donor, gestational surrogate, or any combination of the above. She recruits and screens the egg donors for our in-house donor program as well. She loves working with intended parents and is passionate about third party reproduction and the important role it plays in helping patients achieve their dream of starting or extending their family. She is a member of SEEDS - the Society for Ethics for Egg Donation and Surrogacy.

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