Freezing Eggs to Beat the Biological Clock

May 23, 2006 — -- Megan Griswold is beautiful and bright, with a thriving acupuncture practice in Seattle and degrees from Columbia and Yale. She is also single.

Griswold, 37, had envisioned herself married with children by age 36. But as millions of women from the "Sex and the City" generation know all too well, relationships fail, plans change, and sometimes finding Mr. Right or climbing the corporate ladder takes longer than expected.

To see more on this story, watch "Nightline" Tuesday at 11:35 p.m. ET.

Megan knows what many women her age don't, mainly because it's not part of a woman's typical gynecological checkup: that her egg quality will drastically decrease as she gets older, so much so that by age 40 she has only a 10 percent chance of getting pregnant using her own eggs. Uncertain where things with her then-boyfriend were headed, she took a radical step to try to stop her biological clock in its tracks. She froze her eggs.

"I was starting to get to that age where I was feeling the real desire to go ahead and be a mother, and our relationship wasn't at the point where he was certain that he wanted to do that, and we weren't talking about being married, and so it was enough on my mind that I thought, well, I'm going to look into what I can ... I mean, men don't have the same concern," Griswold said.

Egg freezing -- the scientific term is oocyte cryopreservation -- isn't an entirely new concept, having several years ago become a way for women to try to preserve their fertility after chemotherapy. Back then, however, the procedure's success rates were low because, unlike a fertilized embryo, the egg cell is filled with water. When frozen, the egg forms ice crystals that then damage its integrity when thawed.

That changed in 2005 when scientists in Italy, spurred on by the country's strict laws restricting the freezing of embryos but permitting the freezing of unfertilized eggs, found a new method of freezing and thawing the eggs that kept them more intact.