Infertile women have been offered new hope after scientists found that a common cancer drug triggers the development of new eggs, an outcome which was previously thought to be impossible.

In a discovery hailed as "astonishing", researchers at the University of Edinburgh proved it is possible to reverse the clock and coax the ovaries back into a pre-pubescent state where they begin to produce new eggs.

Women are born with all their eggs, which is why conceiving becomes harder with age, because the eggs grow old, become damaged and eventually run out entirely.

But scientists noticed that women who had undergone chemotherapy for Hodgkin’s Lymphoma with a drug combination known as ABVD had up to 10 times the number of eggs as healthy women.

Far from damaging the chance of having a baby, the cancer drugs may actually have improved their fertility.

The researchers speculate that the shock of chemotherapy may trigger stem cells in the ovaries into producing new follicles, the hollow hair-like structures which each produce a single egg.