British MPs are to debate the controversial issue of mitochondrial donation in the Commons next week. A change in the law could allow IVF babies to be born with the DNA from three different people.

The treatments seek to replace defective mitochondrial DNA (mDNA) in a birth mother's egg with healthy mDNA from another woman in order to limit hereditary mitochondrial diseases.

But how does it even work?

New research has suggested it could potentially help almost 2,500 women of reproductive age in the UK, but it's not without opponents.

Rev Dr Brendan McCarthy, medical ethics adviser to the Church of England, warned against any change in legislation, according the Daily Telegraph.

"The Archbishops' Council, which monitors this issue, does not feel that there has been sufficient scientific study of informed consultation into the ethics, safety and efficacy of mitochondria transfer," he said.

 "Without a clearer picture of the role mitochondria play in the transfer of hereditary characteristics, the Church does not feel it would be responsible to change the law at this time."

The new regulations being debated "make provision to enable mitochondrial donation" under the Human Fertilisation and Embryology Act.

Scientists at the Wellcome Trust Centre for Mitochondrial Research at Newcastle University are among those pioneering mitochondrial donation and will be the first to offer the treatment if it gets the go-ahead.

A study from the group published in the New England Journal of Medicine suggests that 2,473 women in the UK and 12,423 in the US, aged between 15 and 44, are at risk of passing on a potentially lethal mitochondrial disease to their children.