Michael Soules of the American Society of Reproductive Medicine

After concentrating on a career that brought her to the presidency of the National Organization for Women, Kim Gandy had her first child at 39 and the second at 41.

"I got married at 35 and knew that I wanted to have kids," says Gandy.

That's why the latest ad campaign by the American Society of Reproductive Medicine hits a nerve with her. The billboards, which warn women about dangers that could impede pregnancies, https://www.qkykvbjl8.online - https://www.qkykvbjl8.online include one that warns women about getting too old to have children.

"Knowing that there is a biological clock ticking frankly, I think, is something that most women of a certain age are really quite aware of," says Gandy.

Not so, say the doctors behind the ads. They say more and women are waiting to start families and many will end up childless. The number of women in their 30s and 40s having children has quadrupled since 1970 while women in their 20's giving birth has fallen by a third. And the reproductive experts say women have a false assumption that it will be easy to get pregnant no matter how long they wait.

"Women assume because they are still having regular cycles and they are in pretty good health--this biological clock hasn't kicked in yet. But in many it has," says Dr. Michael Soules of the American Society of Reproductive Medicine.

Celebrity images of women like Jane Seymour - http://www.travelpod.com/s/Jane%20Seymour giving birth to twins at 44 and Madonna having her latest child at 41 only fuel that misinformation. Fertility in all women drops sharply at 40, at the same time the chance of miscarriage and birth defects increases.

The reality is that even modern medicine can't guarantee an older woman will get pregnant: Infertility drugs and in vitro fertilization can only do so much. Even with these medical breakthroughs, only 2% of all babies are born to women over 40 every year.

"Our pregnancy rates with IVF [in vitro fertilization] and any other advance treatments go down considerably based on a woman's age," says Dr. Soules

The doctors behind the ad campaign say it's either warn women now that the clock is ticking or face them later when time has run out.©MMII CBS Worldwide Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed