'Three-parent babies': IVF technique should not yet be used to create girls, report says

A controversial IVF technique that produces embryos with genes from three people should not be used to create baby girls until more is known about the safety implications, a report by a high-level group of American academics has concluded.

The so-called “three-parent” embryo technology should initially be confined to male embryos only because of the risk of creating “genetically modified” girls that will pass on defective DNA to subsequent generations, according to the US National Academies of Sciences, Engineering and Medicine (NAS).

The recommendation, in a new report published, contradicts the official position of Britain’s fertility watchdog, the Human Fertilisation and Embryology Authority (HFEA), and the Department of Health which have supported the use of the technique of mitochondrial transfer in the birth of both boys and girls.

Britain is the first country in the world to legally allow the use of mitochondrial transfer in IVF fertility treatment and a research team at Newcastle University is understood to be close to receiving permission from the HFEA to create IVF embryos of either sex for transferring to the wombs of women at risk of passing on mitochondrial diseases to their children.

The United States is also considering mitochondrial transfer but the NAS has concluded that the technology is “ethically permissible” for the avoidance of mitochondrial disease “as long as significant conditions and principles are met”, such as limiting the technology to the birth of baby boys only until further safety work is carried out.

Mitochondria are like the “power packs” of the cells and contain their own genes. They are passed solely down the maternal line from mother to offspring, which means that a ban on creating female IVF embryos with mitochondria supplied by a donor egg would limit the impact of any problems on subsequent generations because male offspring are incapable of passing on any defective mitochondria, the NAS report says.

“The committee recommend that any initial MRT [mitochondrial replacement therapy] clinical investigations focus on minimising the future child’s exposure to risk while ascertaining the safety and efficacy of the techniques,” the report says.

“The recommended restrictions and conditions for initial clinical investigations include…transferring only male embryos for gestation and to avoid introducing heritable genetic modification during initial clinical investigations,” it says.

The NAS report recommends that safety and follow-up studies of any boys born from the technique should be completed before researchers are allowed to use the technique of mitochondrial transfer on creating female IVF embryos for transplant into the womb of women undergoing the treatment in order to prevent mitochondrial diseases in their children.

The report also states that mitochondrial transfer, which results in embryos inheriting genetic material from three people (mother, father and egg donor) is a form of genetic modification, particularly when IVF females are created using the technique because of the ability to pass the “germline” genetic modification to subsequent generations.

The report says that genetic modification means changes to the genetic material within a cell, rather than just the nuclear chromosomes of the cell, which is the alternative definition used by scientific advisers in Britain. The NAS says there is a “novel combination” of genes from three people that would not exist naturally, which is why mitochondrial transfer in female embryos results in “germline” genetic modification.

“As a form of genetic modification of germ cells [eggs and sperm], MRT raises concerns about interference with nature, ‘playing God’, eugenics, and the potential impact on persons with disabilities,” the NAS report says.

Human genetic modification, whether heritable or not, through the use of mitochondrial transfer and the creation of “three-parent” IVF embryos warrants “significant caution and the imposition of restrictions rather than a blanket prohibition” of the technique to prevent transmission of mitochondrial diseases, the NAS says.

Professor Jeffrey Kahn, the chair of the NAS committee behind the report, said: “The limitations on mitochondrial replacement therapy that we propose focus on protecting the health and well-being of children born as a result of the techniques.”

A scientific review of mitochondrial transfer for the HFEA in Britain, published in 2014, did not recommend the selection of male embryos only when using mitochondrial transfer, arguing that it would reduce the number of embryos for transfer to the womb, and so decrease the efficiency of the technique, making it more likely that prospective parents would have to undergo repeated IVF treatment cycles.