The kind of light commonly used in IVF clinics could damage the development of human and other animal embryos in research, according to a study in the Proceedings of the National Academy of Sciences. Even a few minutes’ exposure to sunlight and cool-white fluorescent lights damages mice embryos, says Ryuzo Yanagimachi, of the University of Hawaii.

Cool-white fluorescents, which are blue-white in appearance, are commonly used in office environments. Warm-white lights, which are yellow-white in colour and popular in residential settings, resulted in “far more” eggs developing into babies, Yanagimachi said. The study focused only on mouse embryos, but it is quite possible that human embryos could be affected as well, says Professor Yanagimachi.

He suggested that clinics should ensure that exposure to light is minimised during egg collection and insemination, and while fertilised eggs are examined before being transferred into the womb. “People do not pay much attention to light as a negative environmental factor,” he said. Light exposure apparently places stress on the embryo, which responds by producing increased levels of radical oxygen that are toxic to cell structures.