Alejandro Chavez-Badiola: director of New Hope Fertility Center Eduardo Verdugo/AP/PA

Many more three-parent babies will soon be on their way. A clinic in Mexico is planning to use the technique in 20 pregnancies in the first half of 2017, according to its medical director Alejandro Chavez-Badiola.

The first baby to be born using such a technique to prevent passing on genetic disease was born this year. Test results yet to be published have revealed that the baby boy is perfectly healthy, New Scientist has been exclusively told.

The idea is that the technique, called mitochondrial replacement, avoids harmful mitochondrial mutations passing from the mother to her children. It works by removing the nucleus from a mother’s egg and inserting it into a donor egg, which has its own nucleus removed. The egg is then fertilised with the father’s sperm.


In this way, an embryo gets chromosomes from its mother and father, but the DNA in the mitochondria comes from the donor. The hope is this should enable children not to inherit harmful mitochondrial mutations from their mothers, but will mean that they have genetic material from three people – the father and two women.

Desperate families

The baby born this year is now 8 months old. To create him, Chavez-Badiola and colleagues at the New Hope Fertility Center Mexico manipulated and implanted the embryo in 2015.

All the tests done so far suggest the treatment has worked and the boy is perfectly healthy. “Based on this mutation load, I don’t think he will have any problems,” says Taosheng Huang of Cincinnati Children’s Hospital Medical Center, who has been doing the genetic analysis for the team. Full details are due to be published in coming weeks, he says.

Since news of the birth was first reported, the team has been contacted by many would-be parents whose children risk inheriting the same kind of disorder. “There’s so many desperate families looking for help,” says Huang.

But should clinics hold off until we have more information about whether the technique is safe? “I think they should treat more patients,” says Jacques Cohen of fertility company Reprogenetics, whose team created the first three-parent babies in the 1990s as a result of an experimental fertility treatment. “But how many patients do you treat and how long do you wait until you do more? I don’t have the answers.”

Inherited disease

The parents of the boy born this year sought the team’s help after having two children who died from Leigh syndrome, which is caused by mutations in mitochondria. About 50 to 60 per cent of the mitochondria in each cell have to carry these harmful mutations for children to develop the syndrome.

It is not yet clear how effective mitochondrial replacement is. When the nucleus is transferred from the mother to the donor egg, it carries with it some of the mother’s mitochondria. Lab studies suggest that in around 1 in 20 cases, children could still end up with a high enough proportion of their mother’s mitochondria to cause disease.

But Huang has confirmed that most of the boy’s mitochondria come from the donor. His team has tested cells from many different parts of his body: hair follicles, saliva, cheek swabs, blood, umbilical cord, urine and foreskin. In some tissues, no mutant mitochondria were detected at all. Most had 3 to 4 per cent mutant mitochondria, while the highest level was 9 per cent.

That is far below the level that causes Leigh syndrome, and the mother has seen no signs of the problems that her other children had. “I am very happy to see the outcome,” says Huang.

Treatment in Mexico

The clinic is now working with other would-be parents, Chavez-Badiola told New Scientist, although Huang says the final decision to proceed with further treatments has not yet been taken.

It is likely that none of the parents will be from Mexico, although Chavez-Badiola says he would like to treat local patients as well.

Mexico has no specific regulations governing mitochondrial replacement or assisted reproduction. But Chavez-Badiola dismisses the suggestion that the procedure is being done in Mexico to avoid regulations elsewhere. “It is wrong to say there are no rules in Mexico,” he says. The procedure to produce the boy was approved by an ethical committee, and the clinic is overseen by a regulatory agency. “I am meeting with the government next week,” he says.

Wider use

Huang says the team has also been in discussions with the US regulator, the Food and Drug Administration, about allowing the procedure to be done there, but progress has been “very minimal” so far.

In 2015, the UK became the first country in the world to specifically make mitochondrial replacement legal. The UK’s regulator will decide whether it is safe enough to proceed on 15 December. If they decide to let it go ahead, the country’s first three-parent babies are likely to be conceived in 2017.

In the Ukraine, three-parent baby methods are being used as a fertility treatment, rather than to prevent disease. A recent scientific report concluded that there is no evidence to suggest such techniques improve women’s chances of having children.

Cohen does not support its use for fertility either. IVF success rates are much better now than in the 1990s, he says, so there is much less justification for trying experimental techniques.

Read more: Everything you wanted to know about ‘3-parent’ babies; Should fertility clinics offer experimental unproven treatments?

A brief history of three-parent babies: