DENVER -- Doctors believe a tough economy may be boosting business at sperm banks and egg donation centers as Coloradans search for unusual ways to make extra money.

Betsy Cairo, director of CryoGam Colorado, a Loveland sperm bank, said the number of donor applications coming into her office has spiked exponentially over the past few months.

"All last year, we had maybe 150 applicants," Cairo said. "We had 172 this month."

Since September, more than 400 applications have come in.

Cairo said it's not just cash-strapped college students who are applying either.

"We're getting a wide range of people who apply," she said.

Cairo chalked it up to the slumping economy.

“When things were really good and [people] were making money faster doing other things, we did not have as many applications," she said.

Doctors at fertility clinics have also seen a spike in applications from prospective egg donors, albeit a smaller one.

"We have, in the last several months, seen a slight increase in the number of women who have contacted us to volunteer to become egg donors," said Dr. Eric Surrey with the Colorado Center for Reproductive Medicine.

Surrey said earning money is part of being an egg donor, but he stressed that applicants should have other motivations for donating.

"This is a process that takes quite some time and involves a rather thorough screening," Surrey said. "We really want there to be a reason beyond just finance for doing this."

Surrey said a prospective egg donor must undergo a battery of physical and psychological screenings before being considered and must provide three generations' worth of family medical history. Once selected there are fertility drug injections, blood tests, ultrasounds, physical exams and a minor surgery to remove the egg.

Egg donors can earn in the ballpark of $10,000 for their time and effort.

Cairo said the process to donate sperm is similarly stringent. Applicants have to fill out a 17-page questionnaire which includes essay questions, pass in-depth physicals, including blood tests, and submit semen samples over several weeks.

It can take more than a month before the process is complete and once an applicant is accepted, the commitment is relatively long-term.

"We ask for a once-a-week commitment for at least six months to a year," Cairo said.

Cairo would not reveal how much a sperm donor can earn.

Both Cairo and Surrey stressed that despite an influx of applicants, acceptance rates remain low because of their stringent standards.

Surrey estimated that between 10 percent and 15 percent of egg donor applicants are accepted. Cairo said of her 400 applicants since September, only four have been accepted.