Researchers have identified a drug that extends egg viability in worms, even when taken midway through the fertile window, which could potentially extend a woman's fertility by three to six years.

"One of the most important characteristics of ageing is the loss of reproductive ability in mid-adulthood," said Coleen Murphy, Professor at the Princeton University in the US. "As early as the mid-30s, women start to experience declines in fertility, increased rates of miscarriage and maternal age-related birth defects. All of these problems are thought to be caused by declining egg quality, rather than a lack of eggs," Murphy added. The team used a microscopic worm, Caenorhabditis elegans (C.elegans), as they share many of the genes as humans, including longevity genes.

They found that a group of proteins called Cathepsin B proteases "downregulate", or lead to lower-quality oocytes (unfertilised eggs), as one ages. In the study, published in the journal Current Biology, when the team administered the Cathepsin B inhibitor halfway through the worms' reproductive period, they found that even a late administration of the drug could extend the worms' egg quality. Another experiment that knocked out the cathepsin B genes entirely succeeded in extending worms' fertility by about 10 per cent.

If applied to humans, Nicole Templeman from the varsity said, "It could be a three- to six-year extension of your reproductive period". Reproductive decline is a hallmark of ageing, but despite its prevalence, interventions to slow the loss of reproductive capacity are lacking, researchers said. However, the cathepsin B inhibitor is nowhere near ready for testing in humans, Murphy said, yet it could one day do something mid-reproduction to improve the rest of reproduction.