Safety Concerns Remain Over Three-Person IVF

Later this year, parliament is expected to debate a change to the law that would allow a reproductive therapy called mitochondrial replacement (MR) into fertility clinics. A recent review of evidence by the UK fertility regulator, the Human Fertilisation and Embryology Authority, stated that this experimental technique is "not unsafe". But while the aim of the procedure is noble – to eliminate human mitochondrial diseases, which affect around 1 in 4,000 people – a number of important safety concerns remain unresolved.

Evolutionary theory predicts a mismatch between the DNA in the donor's mitochondria and the mother's nuclear DNA, with potentially serious and unpredictable consequences for any embryo created using MR, an issue my colleagues and I wrote about last year. When MR is carried out experimentally, it has been shown to alter the metabolism and cognitive ability of mice. In other species it results in male sterility, reduced survival, accelerated ageing and changes the expression of many hundreds of genes. But there is a lack of data from species more closely related to humans...