Genetics

Updated 17 March 2015

PGD-IVF testing: what you need to know

PGD stands for Pre-implantation Genetic Diagnosis; IVF stands for In Vitro Fertilisation. Together they are a technique for preventing Huntington’s disease (HD) from being passed on to children.

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PGD-IVF is a form of prenatal testing that makes use of advanced reproductive technology. It avoids the need for termination of a pregnancy in cases where the foetus has inherited the Huntington’s disease gene.

PGD stands for Pre-implantation Genetic Diagnosis; IVF stands for In Vitro Fertilisation. Together they are a technique for preventing Huntington’s disease (HD) from being passed on to children.

The PGD-IVF process
IVF is a medical procedure that involves a woman taking medications to cause the body to produce more eggs than normal. The eggs are then collected and fertilised using a sperm sample from her partner to create embryos in vitro (in a test tube).

The embryos are grown in the laboratory for a few days until the cells have divided into about eight cells. One or two cells are removed from each embryo, and are tested for the HD mutation.

Finally, one or two embryos that don’t have the mutation are transferred to the mother’s womb to allow them to develop. Other healthy, unaffected embryos can be frozen for later use.

About two weeks after the embryos are transferred, a pregnancy blood test is done. If the transfer has been successful, pregnancy continues normally.

PGD can be modified to avoid testing the prospective parents: this allows HD-free embryos to be implanted without the at-risk parent having to learn their HD status.

Disadvantages of PGD-IVF
IVF is time-consuming and can be stressful. The female partner can have a bad reaction to the fertility drugs, and sometimes not enough eggs or embryos are produced. There is also a greater chance of having twins with IVF, which makes pregnancy and delivery more risky for mother and babies.

In addition, during the PGD process embryos can be damaged when cells are removed, and sometimes the HD test fails because there is not enough DNA available. It can happen that all the embryos turn out to be HD negative.

Sometimes only one embryo is available for implantation, or none at all. A pregnancy can fail after implantation.

Each PGD attempt has a 20-30% chance of resulting in a HD-free pregnancy. Women under 35 have the highest success rates.

PGD is expensive, and may not be covered by health insurance.

Information and counselling
Expert genetic counselling is available to help prospective parents understand the options open to you. Genetics services are staffed by clinical geneticists, genetics counsellors and social workers, and can provide you with detailed information and arrange counselling and testing if required.

(Olivia Rose-Innes, Health24, December 2013)

Sources:
Daley, A. Huntington’s Disease Society of America. Family Planning and Huntington’s Disease: Considering Options and Making Decisions.
National Genome Research Institute. National Institutes of Health. Is there a test for Huntington's disease?

 

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