Regulators in the UK have approved genetic experiments on human embryos – the latest step in better understanding and controlling reproduction.

A British government regulator, the Human Fertilisation and Embryology Authority (HFEA), has become the first authority in the world to consider the DNA-altering techniques for use in embryos and approve them.

The news has prompted widespread concern from those opposed to medical advances, who parrot fears about ‘unnatural’ children and ‘designer’ babies.

The HFEA has given its backing to the same process that caused controversy last year, scientists in China announced they had performed gene editing in human embryos to correct a gene linked to a blood disorder.

In the UK, the experts say they will be more open.

“China has guidelines, but it is often unclear exactly what they are until you've done it and stepped over an unclear boundary,” Prof Robin Lovell-Badge, a scientific advisor to the HFEA, told the BBC.

“This is the first time it has gone through a proper regulatory system and been approved.”

The British experiments seek to understand the earliest part of human development, and shed some light on what causes miscarriages.

The actual editing is performed on an embryo seven days after fertilisation.

During this time, the fertilised egg transforms into a structure called a blastocyst; a cluster containing 200-300 cells.

Less than 50 out of every 100 fertilised eggs reach the early blastocyst stage, 25 implant into the womb and only 13 develop beyond three months.

As blastocysts, the cells become organised to perform a range of specific roles – such as forming the placenta, the yolk sac and ultimately, a baby.

While it is clear that some sections of DNA are highly-active at this early stage, much of what they are doing remains a mystery.

It is assumed that genetic expressions at the time guide early development, but it is not known what happens or what goes wrong in miscarriage.

So, researchers at the Francis Crick Institute in London have been allowed to alter these genes in donated embryos to see what roles they might play, and will then destroy the experiments after seven days.

The HFEA also ruled that it would be illegal for the scientists to implant the modified embryos into a woman.

The research team will be led by Dr Kathy Niakan, who has conducted studies in the field for over a decade.

“We would really like to understand the genes needed for a human embryo to develop successfully into a healthy baby,” Dr Niakan explained earlier this year.

“The reason why it is so important is because miscarriages and infertility are extremely common, but they're not very well understood.”

The decision has outraged anti-GM campaigners.

“This research will allow the scientists to refine the techniques for creating GM babies, and many of the government's scientific advisers have already decided that they are in favour of allowing that,” said Dr David King, the director of Human Genetics Alert.

But experts have praised the regulators’ rational approach.

“The use of genome editing technologies in embryo research touches on some sensitive issues, therefore it is appropriate that this research and its ethical implications have been carefully considered by the HFEA before being given approval to proceed,” said Dr Sarah Chan, from the University of Edinburgh

“We should feel confident that our regulatory system in this area is functioning well to keep science aligned with social interests.”