One day later this year, a doctor at a South Florida clinic will freeze a batch of eggs freshly harvested from a woman's ovaries.
Months or years later, when the woman wants to get pregnant, the doctor will thaw a few of the eggs, fertilize them with sperm and inject them into the woman's uterus.
The process will cost about $10,000, and it probably won't work.

The woman will know this; the doctor will have told her that she'll likely have less than a one in five chance of success. But, for one of several reasons, she will have decided the longshot is worth the money.
She might be a cancer patient about to begin chemotherapy or radiation treatments that will leave her infertile.

She could be frustrated by her inability to get pregnant, but morally leery of in-vitro fertilization, a laboratory process that results in unused embryos that must be destroyed, donated to science, put up for adoption, or perpetually stored in a doctor's freezer.

Or maybe the woman will simply want to put her biological clock on hold by keeping healthy eggs in cold storage until she's ready for motherhood.
''We're going to freeze your eggs,'' says Dr. David Hoffman of IVF Florida Reproductive Associates in Margate, one of at least three South Florida clinics that plan to begin offering the procedure on a limited basis this year. ``We can't guarantee that you're going to have a kid from them.''

IN-VITRO FERTILIZATION

Since the first test-tube baby was born in England in 1978, the fertility business has boomed. In 2003, nearly 50,000 U.S. babies were born via in-vitro fertilization, or IVF.

In a typical IVF cycle, a woman who has been unable to conceive takes drugs that prompt her ovaries to produce multiple eggs. A doctor retrieves the eggs -- usually somewhere between six and 20 of them -- and fertilizes them in the lab with the father's sperm, producing microscopic embryos.

A few of the embryos are injected into the woman's uterus; the rest are frozen for future use. That future is often not-too-distant -- more than half the time, the injected embryos fail to implant themselves in the mother's uterus, or they implant but the mother has a miscarriage. In those cases, many patients choose to retrieve the frozen embryos and try again.

In egg freezing, the first steps are the same -- a woman takes drugs to stimulate egg production, and a doctor retrieves as many eggs as possible. But, unlike in IVF, the eggs are then frozen unfertilized, not to be thawed until the woman is ready to have a child.

The theoretical difference couldn't be simpler: Fertilize the eggs after you freeze them, not before. But that difference can be profound.
It means a woman who believes an embryo has the moral status of a child doesn't need to embark on a procedure that can result in frozen, unused embryos. It also means a woman who could soon be rendered infertile by a cancer treatment or by aging may be able to preserve her ability to have a child -- even if she doesn't yet know who the father will be.

''Just imagine if you are a young lady, career focused,'' says Harold F. Rodriguez, who runs the assisted reproduction lab at the Center for Advanced Reproductive Endocrinology in Plantation, which will soon offer egg freezing. 'You can basically make your own reproductive choices. You can say, `I'm going to freeze my eggs now and later on, if I do want to have kids, I don't have to go through what a lot of other women go through.' ''

But while freezing embryos has been routine for decades, freezing eggs has proven more difficult.

''We've been trying to be able to freeze eggs for the last 25 years,'' says Dr. Kevin Winslow, whose Jacksonville clinic was among the first in the nation to offer the procedure, and claims some 40 births from frozen eggs.
(Some of Winslow's peers note that he has not published his results in the peer-reviewed medical literature, the traditional venue for establishing scientific accomplishments. ''You can't go by what somebody says; you have to go by what's in the literature,'' Hoffman says.)

The egg is the largest cell in the body, and full of water -- which tends to crystallize upon freezing, damaging key structures in the cell. In the past decade, researchers have chased multiple strategies to avoid this problem, with some success. Experts estimate that the world now counts some 200 people in Europe, Asia and the United States born from thawed eggs.

While those results are encouraging, the numbers are still too low to be sure that freezing eggs doesn't increase the risk of birth defects, according to a 2004 position paper published by the American Society for Reproductive Medicine.
The procedure seems to be working in people, and has been done extensively -- and successfully -- in animals, said Dr. Michael Jacobs, whose Fertility and IVF Center of Miami will likely offer egg freezing to some cancer patients later this year. But caution is still appropriate, he said.

''In the animal models it doesn't seem to be a problem, but nobody cares if their cow goes to college,'' he said.

The ASRM paper said egg freezing should be conducted only as an experimental procedure and should not ''be marketed or offered as a means to defer reproductive aging.'' That is, it should not be done for women who simply want to put their biological clock on hold.

Some doctors disagree.

''Any woman approaching age 36 should be strongly encouraged to go ahead and try and start her family as soon as possible,'' Winslow wrote in an e-mail interview. ``If that woman is not in a position to do so, I think there is enough reassuring data to make [egg freezing] a viable option.''

Mitzi Hamby was among Winslow's first egg-freezing patients. She and her husband went to see Winslow when she was 34, after trying to get pregnant for six years. They were wary of freezing embryos.

''In our Christian belief, life begins at conception,'' she says. She told Winslow: ``I can't have children in a freezer, and I can't give them up for science and I can't give them up for adoption.''

Winslow retrieved 22 eggs from Hamby's ovaries. They fertilized some of the eggs and injected them into Hamby's uterus. They froze the remaining 16 or so unfertilized eggs. Hamby miscarried about three weeks into her pregnancy.
They then turned to the frozen eggs. Winslow thawed them; six were in good shape. After fertilization, four appeared to be viable embryos. Winslow injected those into Hamby's uterus.

Today she has healthy 7-year-old twin girls, born of the once-frozen eggs.
Doctors hope stories like Hamby's will proliferate in the coming years, as more data emerges, success rates improve and egg freezing moves into the mainstream.

''The benefit is huge,'' Jacobs says. ``There's no question that's what's on the horizon in the assisted reproductive arena in the next few years. This will be part of what we can offer people.''