The technique was used in an attempt to prevent 'embryo arrest' – a problem in which IVF embryos fail to develop past the two-cell stage.
Dr Valery Zukin, director of the Clinic of Reproductive Medicine in Kiev, told New Scientist that the pregnancies are progressing well so far. 'One, a girl, has now reached 26 weeks, and a boy has reached 20 weeks,' he said. His team also presented their results at the American Reproductive Technology Congress in New York last week.
The Ukrainian team used a technique called pro-nuclear transfer (PNT). Two eggs – one from the mother and one from a donor – are fertilised, and the nuclear material from the mother's embryo is transferred to the donor's embryo. The newly created embryo gets all of its nuclear DNA from its mother and father, but its mitochondrial DNA is inherited from the donor.
The report follows the announcement by Dr John Zhang of the birth in Mexico of the first healthy baby conceived through mitochondrial donation (see BioNews 871). In that case the maternal spindle transfer technique was used to avoid the baby inheriting potentially fatal mitochondrial disease.
Back in 2003, Dr Zhang used PNT in an attempt to treat embryo arrest, theorising that something in the egg cytoplasm itself was preventing the embryo from developing. After much controversy, he finally published his research 13 years later (see BioNews 865).
Although all three fetuses created were later lost, Dr Zhang said that analysis showed that they were healthy, suggesting the technique could be safely used. Dr Zukin in the Ukraine says that early DNA tests on the current fetuses also show that they are genetically healthy.
But there is concern about extending mitochondrial donation to treat infertility. Dr Dean Betts of Western University in Canada says that no one really knows why embryos arrest. 'It doesn't mean the underlying reason why the embryo arrested in the first place is gone, possibly allowing development of an abnormal embryo,' he told New Scientist. 'I think it's too risky. I highly recommend banning this procedure in humans as we don't know enough to ensure its safety.'
Sarah Norcross, director of the Progress Educational Trust, which publishes BioNews, told BBC Radio 4's Today Programme: 'We need to be clear, there are two situations here. Where people are trying to avoid passing on inherited mitochondrial disease, that's one thing. Those women are usually fertile, and they're trying to avoid having a baby with this very serious condition. When we're talking about going overseas because you're failing to get pregnant, because you've got an infertility problem, then it's quite different. There doesn't seem to be any evidence that this works. You're at best wasting your money, and at worst putting yourself at risk.'
The UK is the only country in the world to have introduced legislation specifically allowing mitochondrial donation (no licences have yet been issued), but the law only allows the technique to be used to prevent mitochondrial disease.