An explosion of tiny sparks erupts from the egg at the exact moment of conception.

Scientists had seen the phenomenon occur in other animals but it is the first time is has been also shown to happen in humans.

Not only is it an incredible spectacle, highlighting the very moment that a new life begins, the size of the flash can be used to determine the quality of the fertilised egg.

Researchers from Northwestern University, in Chicago, noticed that some of the eggs burn brighter than others, showing that they are more likely to produce a healthy baby.