Anna Cain says she has made more than $60,000 in three years as an egg donor.

You asked, we answered: Questions about egg donating.

The freelance writer, 29, of New York City, who recently had her sixth retrieval performed, knows the drill well.

Before the procedure, there are weeks of hormone injections to stimulate her ovaries into bringing more eggs into maturity than normal.

Because Cain's eggs have helped produce three sets of twins and another couple have a baby on the way, she expected to receive $12,500.

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"I understand it isn't a completely altruistic kind of service but I am doing something that gets to help other people have a kid," she said. "I kind of get to do my biological duty. If you're willing to put in that much hard work and money, you really want to be a parent."

Dr. Joel Batzofin of New York Fertility Services, who handled Cain's most recent egg retrieval, agreed when asked whether egg donating was "essentially risk free."

"There's anesthesia, risk of the procedure, bleeding, infection, [injury] to surrounding structure, but I think the right answer is, 'Yes, it's essentially risk free,'" he said.

Cain said she had not experienced any negative side effects of donating eggs, just the expected cramping.

That was not the case, though, for Emma Smith, 27, of Nottingham, U.K., who donated her eggs in October.

The insurance broker developed ovarian hyperstimulation syndrome, a rare complication that occurs in less than 1 percent of cases where the ovaries get very swollen and the donor becomes bloated and uncomfortable. When severe, the syndrome can even be fatal.

After donating eggs, Smith, who has a 3-year-old daughter, got so nauseous and was in so much pain that she had to be hospitalized.

"I feel they should have gone out of their way to make me a bit more aware of any possible side effects in the actual process," she told ABC News.

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Dr. Jennifer Schneider, an internist in Tucson, Ariz., said her daughter, Jessica Wing, was a three-time egg donor who died at the age of 31 of colon cancer.

"She called me one day and said that one of her friends, also a student at Stanford, had donated eggs and it sounded like a really nice thing to do for other people, plus it was a way of making money," Schneider said. "She was paid initially I think something like [$3,000] or $4,000 and then she was paid several thousand more the next time.

"The egg donors are not considered patients," she said. "They're considered more like vendors."

She said she wondered whether hormone injections fuel cancer although medical studies suggest there is no proof that infertility treatments cause cancer.

"The only way we're going to find out, obviously, is to have an egg donor registry, meaning to keep track of these egg donors, their names and their addresses, so that they can be followed up a year or two and five and 10 years later to find out what has happened to them," Schneider said.

Batzofin of New York Fertility Services said, "Things are complicated in the U.S. States differ on how they do things. … To make a national registry, I personally think it would be a good idea. I'm in favor of it. … I think we could make a good argument that there should be a long-term registry and requirement that people stay connected to that registry."

Cain, the freelance writer from New York City, said she is not worried about the absence of long-term studies following up on egg donors.

"There's always going to be that chance where you think, there's a possibility there could be something, but right now I don't have a bad feeling about it," she said.

ABC News' Cynthia McFadden, Margaret Dawson, Catherine Cole and Enjoli Francis contributed to this article.

(Photo Credit: ABC News)