For Women Who Want Kids, 'the Sooner the Better': 90 Percent of Eggs Gone By Age 30

Jan. 29, 2010— -- By the time a woman hits 30, nearly all of her ovarian eggs are gone for good, according a new study that says women who put off childbearing for too long could have difficulty ever conceiving.

The study published by the University of St. Andrews and Edinburgh University in Scotland found that women have lost 90 percent of their eggs by the time they are 30 years old, and only have about 3 percent remaining by the time they are 40.

It's common knowledge that women have more difficulty conceiving as they age, but this is the very first study believed to quantify the number of eggs lost and it shows that the decline is more rapid than previously believed.

Over time, the quality of ovarian eggs also deteriorates, increasing the difficulty of conception and the risk of having an unhealthy baby.

The study was based on information collected from 325 women of varying ages in the United Kingdom, the United States and Europe.

Dr. Marie Savard, "Good Morning America" medical contributor, visited "GMA" to discuss the issue and its implications for moms-to-be.

"Women lose eggs a lot faster than we thought," she said. As you get older, conceiving is "much more difficult. ...Even all those assisted reproductive techniques are challenges."

"That biological clock does tick," she said, adding that her advice to women who want kids is, "the sooner the better."

Q: Is there anything you can do to slow down the loss of fertility?

A: You can't reverse the biological clock, but Savard said there are certain factors within your control that have an impact upon your fertility.

For example, stopping smoking, keeping your weight down and controlling stress can all slow the loss of fertility.

Women who have more pregnancies are fertile for longer, and some women are born with more eggs than others, she said. The more eggs with which a woman is born, the longer she will be fertile and more time she will have until the onset of menopause.