Brett Molina and Elizabeth Weise

USA TODAY

Silicon Valley is known for offering incredible job perks, but the latest moves by Apple and Facebook could help the companies attract more female employees.

Facebook said it offers egg freezing for female employees up to $20,000. The company also offers adoption and surrogacy assistance and "a host of other fertility services for male and female employees," the company said via e-mail.

Apple also offers egg freezing and storage, extended maternity leave, adoption assistance and infertility treatments.

In a statement, the company said "We want to empower women at Apple to do the best work of their lives as they care for loved ones and raise their families."

The benefit is worth close to $20,000. A typical round of egg-freezing costs about $10,000, with $500 or more in fees each year for storage. Two rounds are usually necessary to harvest about 20 eggs, which is considered ideal.

The coverage by Apple and Facebook is part of a growing trend to beef up employee perks at Silicon Valley companies to recruit new hires.

However, the option won't be one every woman will jump at, said Kellye Sheehan with Women in Technology, a professional organization for women in the tech industry.

"This is a nice perk but of course it's a very personal decision for every working woman. When to time college, grad school, babies, starting a career, accelerating a career — all of these have huge ramifications in your life and that of your significant other," she said.

"Is the employer trying to tell us something? Agreed, working mothers have a lot to juggle. But you can't let your employer force you into something that doesn't fit your values or personal choices," Sheehan added.

The idea of freezing eggs for later use was first proposed for cancer patients. Chemotherapy damages a woman's eggs, so removing and freezing eggs of female cancer patients gave them a chance at having children later on.

For what's sometimes called "fertility preservation," the idea is that by removing and fertilizing their eggs in their 20s, women will have a better chance of getting pregnant in their 30s and 40s.

Reproductively speaking, a woman's best chance at a healthy pregnancy that results in a healthy baby is in her 20s.

This is because the viability of a woman's eggs declines over time. Fertility gradually declines in the 30s and drastically beginning around age 35, according to the American Society of Reproductive Medicine.

The actual harvesting of the eggs is not trivial. It requires rounds of hormone injections to coax the body into producing multiple eggs at once. When the eggs mature, they are harvested via a needle inserted through the vagina.

Exactly how successful the woman will be at having a child if she froze her eggs in her 20s and then used them in her 30s or 40s isn't yet known.

"We don't yet have patients who've cryopreserved eggs in their 20s and are coming back in their 30s and 40s, because the technology is so new," said Jennifer Eaton, medical director of assisted reproductive technology at Duke Fertility Center in Durham, N.C.

However centers that are using the new freezing techniques report "comparable pregnancy and live birth rates among women who freeze eggs and come back," she said.

The technology used to freeze human eggs has become much better in the last 10 years and is much more likely to result in the birth of a child than in the past, said Alan Copperman, director of the division of reproductive endocrinology and infertility at The Mount Sinai Hospital in New York City.

"Five years ago, if you'd interviewed me, I would have talked about how much better a fresh egg is than a frozen egg. But in 2014, a frozen egg is almost as good as a fresh egg," he said.

In the past, doctors used a slow freezing technique with eggs. However the egg is the largest cell in the human body and contains a great deal of water. During freezing, ice crystals sometimes form, which damage the spindle apparatus within cells that pulls chromosomes apart during cell division.

Today a quick-freeze process, called vitrification, is used that is less likely to create ice crystals and results in better-preserved eggs, Copperman said.

Egg freezing isn't a guarantee that you're going to have a healthy baby, but could increase the odds, said Marcelle Cedars, director of reproductive endocrinology and infertility at the University of California-San Francisco.

"I always tell my patients it's not a baby in the freezer, it's the possibility of a baby," she said.

No matter how old a woman is when she decides to start a family, frozen eggs are the last resort.

"Even at 40, 50% of 40-year-olds who want to get pregnant get pregnant," Cedars said. "And it's a lot more fun to do it the old-fashioned way."