The Science Behind 'Three-Parent Babies'

Elise Solé
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Photo by Corbis 

Big news: Britain just became the first country in the world to allow couples to undergo a controversial procedure to create “three-parent babies.”

The official term is “mitochondrial donation” (although it’s also called “three-parent IVF”). The treatment, which uses DNA from the mother, father, and a female donor, will help couples with mitochondrial diseases — a collection of severe genetic disorders — conceive without worry of passing the illness to future generations.

While Britain is making news, the controversial treatment is also being researched in the United States. (The U.K. bill passed 382 to 182 in favor of the treatment; it still needs the support of Parliament’s upper chamber. If it passes, couples across the pond could begin treatment in October.)

And while this is hopeful news for couples who are predisposed to genetic disorders, the passing of the law raises more questions in the ethical debate on whether assisted reproductive technology leads to “designer babies.”

Critics of “three-person IVF” (which replaces defective mitochondria in the nucleus of the egg) specifically argue that it could cause an uptick in unnecessary IVF procedures, that the transfer of a nucleus from one egg or embryo into another changes gene function and may cause long-term medical issues for the child including cancer, that the procedure is risky for women with mitochondrial disease (which is rare), and the effectiveness of the treatment is unknown since neither human clinical trials nor follow-up on babies resulting from the procedure would be required.

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Supporters of the U.K. law say the treatment is simply a branch of traditional IVF and that the name “three-parent IVF” is exaggerated. “The biggest problem is that this has been described as three-parent IVF. In fact it is 2.001-parent IVF,” Gillian Lockwood, a reproductive ethicist, told the BBC. “Less than a tenth of one percent of the genome is actually going to be affected. It is not part of what makes us genetically who we are. It doesn’t affect height, eye color, intelligence, musicality. It simply allows the batteries to work properly.”

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Here in the U.S., 2,000 kids develop mitochondrial disease by age 10 and between 1,000 and 4,000 kids are born with some form of the illness. The Food and Drug Administration (FDA) has been considering whether or not to approve trials of three-person IVF since 2013. According to a story published by the Washington Post, U.S. scientists have been experimenting with several types of mitochondrial replacement techniques that have resulted in successful trials in animals and the successful creation of human zygotes.

“We’ve been experimenting with three-person IVF since 2003, however, at the time, the FDA put a stop to it because we didn’t have enough safety data and there was an issue with federal funding because it was tied to the abortion debate,” Art Caplan, M.D., the director of medical ethics at New York University’s Langone Medical Center, tells Yahoo Parenting. What’s more, he adds, many people are uncomfortable with the novel idea of one baby carrying three different sets of DNA.

“The procedure is often associated with ‘designer babies’ but it can’t determine eye color, musical capabilities, or any other superficial traits,” he says. “Three-person IVF simply replaces the battery of a cell — the energy unit — with a healthier one, almost like a mini organ transplant.” According to Caplan, primate studies have been underway in the United States since 2009 and it’s only a matter of time before the technology is available to U.S. couples.

“This treatment wouldn’t be a routine part of IVF,” he adds. “It would help a very specific group of people suffering from a rare illness and that’s a good thing.”

Three-parent IVF isn’t the only controversial treatment that has made waves in genetic testing. Similar medical interventions include pre-implantation genetic screening (PGS), an IVF treatment that screens for genetic abnormalities and the sex of a baby and new, non-evasive blood tests like MaterniT21, which analyzes fetal DNA in the mother’s blood at 10 weeks of pregnancy to determine with 99 percent accuracy whether or not a baby has Down’s syndrome. Such procedures are controversial because critics say they could result in increased abortion rates.

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