For many women juggling work and family aspirations, timing is a big concern. It's a classic case of catch-22: starting a family can disrupt a career, but putting it off might lessen the likelihood of conception. Times are certainly changing; the average age of first-time childbearing has risen by about five years since 1970. But biological clocks still tick, same as they ever have. Since fertility declines with age, waiting too long can amount to a real gamble.

But now there's big news from Boston: A researcher with Massachusetts General Hospital may be on track to slow the ticking down -- or even stop it completely.

Jonathan Tilly, Ph.D., is the director of the hospital's Vincent Center for Reproductive Biology. He's devoted decades of research to women's reproductive health care, and a recent breakthrough could have huge implications for the future of fertility.

As the conventional wisdom goes, girls are born with all the eggs they'll ever have. Those eggs run out, so to speak, when menopause hits. But based on his work, Tilly now suspects that it may be possible to induce the formation of new eggs in adult women.

He made his first shocking announcement in 2004, when he found cells in the ovaries of female mice that had potential to generate new eggs.

Now, recent experiments have proven that human females carry those same cells. Tilly and his team collected ovarian tissue from young women, found cells that looked similar to those they had seen in mice, and eventually developed those cells into eggs.

Right before our eyes, in culture dishes, we were watching that process happen for the first time, said Tilly in an interview with NPR. And when those cells were injected back into ovarian tissue, they still continued to grow. What this means is that little bank account of eggs that a little girl gets at birth is in fact open to continued deposits!

Tilly is optimistic in the hopes that his work will lead to major breakthroughs in fertility treatments. But plenty of scientists in the field are skeptical, noting that it could still be a long while before this work translates into effective treatments. Still others object on moral grounds, wondering whether we should tamper with the fundamental limits of human fertility.

The full report on Tilly's research will be published next month in Natural Medicine. In the meantime, he's working on fertilizing the cells he's created in order to create an implantable embryo.