The new guideline still advises a go-slow approach. It recommends egg freezing for patients facing sterility because of cancer treatment and for couples who object to freezing embryos, but not for healthy women worried about using or losing their eggs.
"We're not saying don't do it" for healthy women. "We're saying, proceed with caution," said Samantha Pfeifer, a University of Pennsylvania fertility specialist who chaired the guideline committee. "For women in their late 30s and early 40s, success rates are not as good" as for younger women.
But in the real world, the brakes are off.
"If it's safe for a teenager undergoing chemotherapy, how are you going to tell a 35-year-old woman no?" asked reproductive specialist Michael J. Glassner, a founder of Main Line Fertility in Bryn Mawr, which has had 50 cryo-egg births. "I think it's unfair to tell someone, 'We know your fertility is declining, but you can't do this.' "
Even more groundbreaking fertility preservation options are under development. At Children's Hospital of Philadelphia, researchers are freezing ovarian and testicular tissues taken from cancer patients as young as 3. The hope - no guarantees - is that by the time these children are ready to have children, the technology they need will be ready, too.
The egg is the largest human cell, 180 times bigger than a sperm cell. It is loaded with fragile genetic structures surrounded by water that can turn into deadly ice crystals. Even an eight-cell embryo is easier to freeze than an egg, because it can lose a cell or two and still develop normally.
Until recent years, scientists had a hard time dehydrating, cryoprotecting, and freezing an egg - not to mention reversing the process - without cracking its shell or scrambling its chromosomes.
The breakthrough, pioneered by Italian and Japanese scientists, was a flash-freezing process called vitrification. Studies show 80 percent or more of vitrified eggs survive thawing, and up to 12 percent of thawed fertilized eggs produce a pregnancy.
Fears of birth defects also have been allayed.
"No increase in chromosomal abnormalities, birth defects, and developmental deficits has been reported" in cryo-egg babies, the reproductive society's guideline says.
About 1,000 births have been reported worldwide since the first in 1986. Though that's still not a lot, 90 percent of those births have occurred since 2004.
"So now we have some safety data we didn't have," Penn's Pfeifer said.
Cost remains a barrier. Removing and freezing eggs runs about $10,000. Annual storage is about $1,000. Add the costs of thawing, high-tech fertilization, and implanting embryos, and having a baby can easily cost $40,000.
Some clinics, including Main Line Fertility, offer deep discounts on egg-freezing to cancer patients.
And health plans may now face pressure to pay for egg freezing, at least for such patients. "Once it loses its 'experimental' tag, maybe insurance companies will cover it," said Jill P. Ginsberg, a pediatric oncologist at Children's Hospital of Philadelphia.
For former Children's patient Courtney John, 27, of Allentown, freezing eggs at age 17 was about hope - hope of beating leukemia, hope for a full future life.
"I am cured, but I am sterile," said John, now a teacher in Boston. "It's nice to have the option of maybe someday having kids."
"But," she added, "I did it out of need, not out of choice."
It remains to be seen whether the reproductive society's stamp of approval will drive up demand for the technology from women who want a hedge against aging. But while freezing can fool Mother Nature, it cannot beat Father Time. Just as with fresh eggs, studies have found the chance of making a baby with frozen ones declines if the woman providing them is of "advanced" age - meaning 35 and older.
Neither egg freezing nor sperm freezing can preserve the fertility of one vulnerable group: cancer patients too young to produce those reproductive cells.
This is a growing issue, Ginsberg said, because with steady improvements in childhood cancer treatment, cure rates are now near 80 percent.
"Now more than ever, it is critical that we address the quality of the lives saved," she wrote in a recent journal article. "Fertility is a qualify-of-life issue of great importance."
She is leading two studies aimed at pushing the reproductive envelope.
One is collecting testicular biopsies from prepubertal boys before they undergo cancer treatment. Half of the tissue is used for research, the other half is frozen for the patient's possible future use.
The hope is that stem cells that make sperm could be extracted from the tissue, matured, and multiplied in lab cultures, then reimplanted in the patient at the appropriate time to restore fertility.
So far, the study has tissue from 40 boys.
"We are so careful to make sure the parents know we are offering no guarantees. We're not sure the technology will ever be available," Ginsberg said. "Even in light of that, 80 percent of parents" agree to participate.
A similar study has collected ovarian tissue from 12 prepubertal girls. Theoretically, the tissue could one day be reimplanted and become functional. Or immature eggs could be taken from the tissue, then matured and fertilized in lab dishes when the girl-turned-woman wants to become pregnant.
In adult women, there are about a dozen reported cases of successful ovarian tissue being frozen and reimplanted, but it is still highly experimental.
"This," Ginsberg said, "is the last frontier of fertility preservation."
Contact Marie McCullough at 215-854-2720 or firstname.lastname@example.org.