“Many of these women took time to finish their educations and establish themselves at work,” she said. “Women figured out early on there is a financial return to delay, and they could provide for their families better.”

But there is a cost to that delay, since fertility drops after age 35. “The chances for chromosomal problems like Down syndrome are overblown in most people’s mind, but they underestimate the chances of getting pregnant (as they get older) or miscarrying,” says Dr. Marjorie Greenfield, professor of obstetrics and gynecology at University Hospitals Case Medical Center.

In fact, the chance of having a baby at age 40 is only about 10 percent, without the help of assisted reproductive technologies. Yet, she is aware too, that having a baby when a woman is younger can have a long-term economic effect on the family.

“I understand it cuts both ways, since I have watched women who decided to have children really young have no economic security and they’ve lost their place in the workforce,” says Greenfield, author of “The Working Woman’s Guide to Pregnancy.” “But it is harder to get pregnant when a woman is older.”