Critics fear that gene-editing human embryos could be used to create designer babies. Picture: Pixabay

London - Pioneering British scientists have identified a key gene that may help to explain why so many IVF pregnancies fail.

Researchers "edited" human embryos to see what happened when they removed the gene, which had been identified during tests on mice.

By extracting the section of DNA, they discovered its key role in preventing failed pregnancies.

As a result, one of the main applications for the research could be to improve IVF success rates.

Most fertilised eggs fail to develop during IVF for reasons that are poorly understood.

It is hoped the study – using surplus embryos donated by women at an IVF clinic – will help the one in seven couples who have difficulty having a baby.

But critics fear that gene-editing human embryos could be used to create designer babies.

Dr Kathy Niakan, who led the work and invented the editing technique, said: "Our research is the first time that genome-editing has been used to understand the role of a gene in early embryonic development.

"This knowledge can be used to improve IVF treatment and improve our understanding of how some pregnancies fail."

After an egg is fertilised, it divides for around seven days until some of the cells cluster together to form a blastocyst, which goes on to become the embryo, while other cells will go on to form the placenta.

Only when an egg successfully reaches the blastocyst stage does it stand any chance of implanting in the womb. During the research, published in the journal Nature, Dr Niakan’s team used a laser to cut a tiny hole in the wall of a fertilized egg before using a microscopically fine needle to inject a protein that "slices off" a piece of DNA known as Oct4.

They then bridged the gap with another piece of DNA.

The team from the Francis Crick Institute in King’s Cross, central London, found that unedited embryos developed normally, but those without the Oct4 section of DNA failed to grow.

Co-author Dr Norah Fogarty, also from the Francis Crick Institute, said: "We were surprised to see just how crucial this gene is for human embryo development."

Strict rules make it illegal to allow such a modified human embryo to develop beyond 14 days or be implanted.