The benefits for a child born after mitochondrial donation - better known as a three-parent baby - are easily demonstrated: no potentially lethal mitochondrial disease. The benefits for its parents are evident in the delight and relief on their faces as they cuddle their newborn. The benefits for the IVF clinic are also clear: unquestioning praise in the media and loosened purse strings for government funding.
But there are costs to this controversial IVF procedure - and these are being ignored by gullible journalists and swept under the carpet by government regulators.
Some women are carriers of defective mitochondrial DNA (mtDNA) which can cause serious birth defects or even death. The procedure attempts to eliminate the defective mtDNA of the primary mother by substituting the mtDNA of a second "mother". A baby conceived with three-parent IVF carries a tiny bit of mitochondrial DNA from the second "mother".
Journalists and politicians often describe this technique as "lifesaving". The UK's Human Fertilisation and Embryology Authority (HFEA) has cautiously endorsed it. "At each stage of the review process the panel reached a view that the evidence it has seen does not suggest that these techniques are unsafe", a report stated in 2014.
The question is "unsafe for whom?" What about the embryos destroyed in the process of creating a disease-free embryo?
Researchers and IVF clinics have been loath to report how many embryos perish in the process of creating a single three-parent baby. In the UK, mitochondrial donation is regulated by the Human Fertilisation & Embryology Authority and the HFEA is notoriously parsimonious about sharing this data.
However, tenacious MPs have requested information on the wastage of embryos. The results are disturbing for anyone who believes that embryos should be respected as human life.
Fiona Bruce MP recently asked how many patients had been authorised by the HFEA to have mitochondrial donation. The HFEA responded that 32 patients had been authorized, that 317 embryos had been created, and that 24 had been transferred to the wombs of these women.
In all cases, the technique used was pronuclear transfer. This is a technique in which the pronucleus, containing both egg and sperm DNA, has been removed and substituted for the pronucleus of a donor embryo.
For many reasons, this headline-grabbing technique is intensely controversial. It is legal only in the UK, Australia, and Singapore. In the United States it is barred by the Food and Drug Administration. It is marketed by clinics in Greece and Ukraine (and perhaps other countries) where there is less regulation and there are fewer scruples.
It is not known how many three-parent babies have been born in the UK. When the news broke in May that a baby had been born with the help of the Newcastle Fertility Centre, the only IVF clinic in the UK licenced to perform the procedure, the HFEA said only that the number of births was "less than five".
Its excuse for this obfuscation was that a precise figure "could lead to the identification of a person to whom the HFEA owes a duty of confidentiality".
However, it appears likely that there is only one.
So the full cost-benefit analysis of the UK's first three-parent baby is probably this: 316 human embryos destroyed to create 1 healthy baby.
But are they sure that this baby will be healthy?
This remains to be seen. MIT Technology Review reported recently that sometimes the technique does not work, with the defective mtDNA re-emerging in the baby's cells, an event called "reversion":
"The scientists behind the work believe that around one in five babies born using the three-parent technique could eventually inherit high levels of their mothers' mitochondrial genes. For babies born to people with disease-causing mutations, this could spell disaster - leaving them with devastating and potentially fatal illness."
Joanna Poulton, a mitochondrial geneticist at the University of Oxford, told the magazine that even a 20 percent risk of reversion was worrying. "There are mutations where quite low levels can cause problems," she says. For some diseases, the level can be as low as 15 percent, she says.
And Heidi Mertes, a bioethicist at Ghent University, said that "Scientists knew beforehand that the trials were never going to be risk free, and that they involve a potential waste of perfectly good donor eggs and embryos. 'In the end, you're presenting an option to patients that is more dangerous than their alternative,' she says."
So, who are the real beneficiaries of the ethically controversial procedure of creating three-parent babies? Not the embryos - hundreds will perish to produce one baby. Not the baby, because it has a good chance of inheriting the mitochondrial disease. Not the parents of the destroyed embryos. Not the parents of the baby, who will be wracked by anxiety over the health of their child.
How about the medical researchers? Yes, they benefit from more publicity, more funding, more publications, and more expertise.
Is it really worthwhile destroying 316 human embryos to keep those medical researchers happy?