IVF technique helps family with MD

The first baby has been born in Europe as the result of a new IVF procedure that checks embryos for genetic disorders. The baby was at risk of inheriting Charcot-Marie-Tooth disease (CMT), a neuromuscular condition which falls under the umbrella of muscular dystrophy.

The baby’s mother and grandfather have CMT which causes weakness and wasting of the muscles below the knees and often those of the hands, and can lead to loss of feeling in the fingers and legs.

The new technique called ‘karyomapping’ has ensured that the next generation in this family will not inherit the debilitating condition. Karyomapping is much faster and potentially cheaper than previously used preimplantation genetic diagnosis (PGD) techniques.

Success using karyomapping was also announced in the USA in January but the details were not made public.

What is preimplantation genetic diagnosis (PGD)?

PGD allows couples that carry certain genetic conditions to have treatment at fertility (IVF) clinics to prevent passing on the condition. This involves couples undergoing standard in vitro fertilisation (IVF) during which eggs are fertilised by sperm in a laboratory. The resulting embryos are then tested in a procedure known as PGD. The embryos are grown in the laboratory for several days and a small sample of the embryo’s DNA is tested for the presence of the genetic change. Only embryos that do not carry the genetic change are transferred back into the woman’s womb.

The first babies were born as a result of PGD in 1990. These first babies were at risk of conditions that only affected boys, and PGD was used to select female embryos for transfer into the mother. In the years following, the technique was further developed to be able to detect the specific DNA change causing the genetic condition, and can now be used to screen for a wide range of conditions affecting both sexes.

PGD is only available if the genetic mutation is known. Using conventional PGD techniques, a new diagnostic test usually needs to be developed for each couple and this can take up to six months. In Australia PGD must be paid for privately.

What is karyomapping?

A new PGD technique called karyomapping has become available in some fertility clinics (including some in Australia). It uses a DNA finger-printing technique to identify which embryos have inherited the chromosome carrying the altered gene. Again, the affected gene needs to be known, but the test is much quicker to set up than previous PGD tests, only requiring a few weeks rather than many months.

Another advantage of karyomapping is that information about the whole genome is obtained which can allow chromosomal abnormalities, such as Down’s syndrome and those which can cause the embryo to fail to implant or to miscarry, to be identified. As a result the embryos with the best chance of producing a healthy child can be selected, potentially improving the IVF success rate.

This advance is an important step forward and gives hope to parents concerned about passing on serious genetic conditions to their children. However, it is important to consider that all IVF procedures can be expensive and stressful and some couples require many rounds of treatment for success.

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Uploaded 3July 2018