Currently around 50 per cent of fertilised eggs do not develop properly and experts believe that faulty genetic code could be responsible.

Some clinics take videos of the egg developing to try pick up problems early, while others check for genetic mutations, but that is an invasive procedure which can damage the tiny egg. Often it is just down to a clinician decided which eggs look the healthiest.

But the new findings could give and extra indication that an egg is flourishing. A video of nine human eggs coming into contact with sperm enzyme showed two flashed much brighter than the rest.

“This is an important discovery because it may give us a non-invasive and easily visible way to assess the health of an egg and eventually an embryo before implantation,” said co-author Dr Eve Feinberg, who took care of the patients who provided eggs for the basic science study and collaborated with the research team.

“There are no tools currently available that tell us if it’s a good quality egg. Often we don’t know whether the egg or embryo is truly viable until we see if a pregnancy ensues.