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IVF technique that tests embryos for genetic disorders has first success

2.0 from 4 votes
Tuesday, August 05, 2014

Doctors in London have reported the first pregnancy in Europe from a new IVF procedure that checks embryos for genetic disorders before they are implanted.

The technique allows doctors to select embryos that are free of dangerous mutations carried by one or both parents even if the precise nature of the genetic defect is unknown.

Fertility specialists at the Centre for Reproductive and Genetic Health (CRGH) said the couple, Carmen Meagu, 26, and her husband Gabriel, had a high risk of passing on a lethal disease to their children. They are now 17 weeks into the pregnancy.

Common embryo testing procedures require months of laboratory work, but the latest tool, known as karyomapping, can be completed within two weeks, meaning a couple can undergo tests without breaking from their IVF treatment cycle.

Meagu's father was badly affected by a condition called Charcot-Marie-Tooth disease, a form of muscular dystrophy, and died in his 50s. She inherited the condition but only has it very mildly. She had a 50% chance of passing it on to her children before the new procedure.

Paul Serhal, the centre's medical director, said the technique, which will be available on the NHS, was likely to replace more traditional ways of testing embryos because it was faster, more powerful and no more expensive. A second couple are 10 weeks into a pregnancy after receiving the same treatment at the clinic.

"Parents at risk of passing on a genetic disorder are faced with heartbreaking implications of potentially creating a life with an inherited illness," Serhal said. "The breakthrough we have achieved means that parents affected may be able to pursue treatment confident that their condition wouldn't be handed down."

The couple have standard IVF treatment to create a set of embryos which are then biopsied. Usually, a few cells are taken when the embryo is a ball of 100 or so cells, though single cells can be plucked from younger, three-day-old embryos.

To perform the karyomapping, doctors first obtain DNA from cheek swabs of the parents and a family member affected by the disorder. The gene sequences are then compared and used to work up a genetic fingerprint for the mutation that causes the disease.

Doctors can then check the cells removed from the embryos and work out which will be affected or not by the disorder, or will be carriers that could pass it on.

The test also checks embryos have the right number of chromosomes, a common cause of miscarriage and developmental disorders such as Down's syndrome. "The short workup time is critical because a woman's fertility may decline rapidly with time. Also, by identifying abnormal sets of chromosomes we can reduce miscarriage rates and increase the number of healthy IVF pregnancies," Serhal said.

"In more than two decades of working this field, this is the single biggest technological leap I have seen. Karyomapping is already making a significant difference to patients," said Dagan Wells at Reprogenetics UK, an Oxford-based company that tested the embryos.

"We believe the CRGH patient is one of the first, if not the first, in the world to receive karyomapping as a frontline clinical test," Wells said. Ten UK fertility clinics offer it to parents.

The procedure could have a big impact on couples who want to have children but are worried about passing on serious genetic disorders that run in their families. Because embryos are tested before they are implanted, the parents do not face decisions about terminating the pregnancy later on. In the UK the procedure can only be used to prevent severe diseases.

"The only embryos transferred to the mother are those that have the correct number of chromosomes and are free of the family's inherited condition," Wells said. "This all but eliminates the inherited disorder from the family and greatly reduces the risk of miscarriage.

"We are entering a golden age of genetics applied to the understanding of infertility, early human development and the diagnosis of inherited disease. Several other major technical advances are now on the verge of routine clinical application and the landscape of IVF is likely to be radically altered in the coming months and years."

Source: The Guardian
2.0 from 4 votes
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