Fertility scientists are excited by the possibility that women may be able to reset their biological clocks. Writing in Nature Cell Biology, researchers from Shanghai Jiao Tong University in China have found that mice have female "germline" stem cells, which theoretically can become eggs. They were able to isolate these cells and culture them. When re-injected into sterilised ovaries, some of the mice became pregnant and produced normal offspring.

This challenges the orthodox view that women are born with a finite number of eggs and cannot generate new ones.

"If true, and especially if applicable also to humans, then this is very important," Professor Robin Lovell-Badge, of the UK’s Medical Research Council told the London Telegraph. "For example, it could provide a means to restore fertility to women who have few eggs or who have had to undergo cancer treatments, by isolating these cells, expanding their number in culture and keeping them frozen until needed for IVF, etc."

However, many scientists urged caution. "The aging process of the human egg differs fundamentally from that of the mouse egg," said David L. Keefe, a professor of obstetrics and gynecology at the University of South Florida, told the Washington Post. "Except at Disney World, humans are not large mice."