Jennifer Dziura, a 28-year-old New Yorker, is one of them.

She received $8,000 to donate her eggs in the fall of 2005 and hopes she'll be chosen again before the private egg broker she's registered with considers her too old. She realizes prospective parents who view her profile might think it a minus that her father is adopted, allowing for little medical history from his side. She also figures some are looking for a blonde, instead of a brunette.

"But, hey, I have perfect SAT scores," Dziura, an aspiring comedian and model, says with a slight chuckle.

As more older moms look for help getting pregnant, younger women have become increasingly willing to part with their eggs. Some do it to help relatives and friends, or from a sense of altruism, but others openly acknowledge money is a big factor in their decision, prompting critics to worry that they're helping drive an unregulated market for human tissue.

In 1996, women in federally monitored programs donated eggs just over 3,800 times. That number has risen steadily, to more than 10,000 in 2004, the most recent year for which the Centers for Disease Control has compiled data.

A decade ago, Dr. Joel Brasch, a fertility specialist in the Chicago area, had to work hard to recruit five or 10 young women for his own practice's donor pool ¡ª but not anymore.

The money is seen as compensation for time and trouble. Among other things, donors learn to inject themselves with hormones and, eventually, have a needle inserted through their vaginal wall so eggs can be harvested.

"Everyone does it for the money," says Dziura, the egg donor in New York. "No one would do that for free ¡ª maybe for your sister, but not for a stranger."

The American Society of Reproductive Medicine, or ASRM, has set a compensation guideline of $5,000, with a limit of $10,000 for special cases ¡ª if, for instance, a recipient wants eggs of rare ancestry.

The president of the Society for Assisted Reproductive Technology, an affiliate of ASRM, argues that if women were just motivated by money, they wouldn't get past the psychological screening to become a donor. And, he says, researchers who've surveyed donors have found another strong motive.

"They're very altruistic and very willing to help a couple who's trying to conceive," says Dr. David Grainger, who's also a reproductive endocrinologist at University of Kansas medical school in Wichita.

Still, some egg brokers ¡ª particularly those in the East and West ¡ª are ignoring suggestions for a cap on compensation, and paying women more.

"Egg Donors Wanted" ads are common on the Internet, in college newspapers and on city trains. And with no federal laws limiting donor fees ¡ª and fertility doctors conceding the difficulties of policing their own industry ¡ª one ethicist says that eggs have quickly become "commoditized."

"It does feel a little more like the Wild West than it ought to," says Dr. Jeffrey Kahn, director of the University of Minnesota Center for Bioethics. And he only sees the problem growing as states such as California move closer to funding major stem-cell research, requiring more donor eggs.

"We worry that we offer people so much money that they are blind to the risk and their motivation is strictly the money," Kahn says.

That's the very reason, he notes, that it is illegal to sell an organ, such as a kidney, for donation. "So I'm not comfortable saying we should start that with human eggs," he says.

A small survey from an Illinois clinic, included at a recent ASRM meeting, found that donors used compensation for everything from savings and down-payments on property to school expenses and car payments. Half of them also used some of the money to pay credit card debt and other loans.

Kristin McKenna, a 25-year-old project manager at a marketing company in suburban Atlanta, donated eggs to help build her savings.

"It does feel weird to know there's a child out there," says McKenna, who's signed up to donate again. "But I'm just a small piece of the puzzle.

"If those two people (who got her eggs) weren't there wanting a child, that child would not exist."

Dr. Lorna Marshall, a fertility specialist in Seattle, says egg recipients often ask to write letters of gratitude to their donors, who remain anonymous in most cases.

But when it comes to money, she asks them to steer clear of donors who get more than $5,000, no matter the circumstances.

Occasionally, Marshall also has had to reject eggs from donors who've been OK'd by a private egg broker, but are younger than 21, the minimum age recommended by the ASRM. The thought is that, by that age, a young woman is old enough to better understand the choice she's making.

But Grainger and some others in the field concede that even the most careful guidelines can't absolutely prevent regrets later in life. That was the case for one young woman who initially told herself she was donating to help prospective parents.

"But if I'm honest, I did it for financial reasons; I wanted to travel," says the 31-year-old woman who lives in New York and works for an international nonprofit. She asked to remain anonymous since her family doesn't know she donated eggs three times.

"It would be a relief to know that my eggs were being used to find medical cures," she says, "rather than being used to produce additional kids for well-to-do American families."