In 2012, the American Society for Reproductive Medicine made a significant announcement: The organization no longer considered egg freezing an “experimental” treatment.

Until that point, the procedure had been mostly reserved for those undergoing chemotherapy or other debilitating medical treatments. That year, the A.S.R.M. opened up egg freezing to those in the larger population who wanted to delay childbearing by preserving their eggs for future use, citing evidence that oocyte cryopreservation led to fertilization and pregnancy rates that were similar to in vitro fertilization.

In the two years that followed, the procedure went mainstream: Facebook and Apple announced they would cover up to $20,000 in costs for their employees, prompting other companies vying to attract and retain top talent to follow suit. Egg freezing start-ups sprouted across the country, throwing egg freezing “parties” and offering quick, free fertility tests in parked vans. The procedure was touted by many as a potential equalizer in the workplace, promising to have as much of an effect on a woman’s life as the contraceptive pill has had.

Over the decade since the A.S.R.M. announcement, the number of people who have frozen their eggs in the United States rose by more than 400 percent, to over 13,000 in 2020 from just over 2,500 in 2012, according to data from the Society of Assisted Reproductive Technology. Most are white, middle-class professionals, and a growing number — roughly 35 percent, compared with 25 percent in 2012 — are women under the age of 35.

“When I was first doing it, the mean age of women who came in was 38,” said Dr. Nicole Noyes, a reproductive endocrinologist and former New York University professor who presented evidence on the effectiveness of egg freezing in 2012 and who now works as a medical director at the egg freezing start-up Kindbody. “Today, most of the consults I’m doing are with women in their 20s,” she explained, and egg freezing conversations that were once “very shame-based” are now seen as routine, she said.

“It’s kind of like online dating,” she added. “It’s just part of life.”

The process, however, is physically, financially and emotionally demanding. Patients take hormone injections once or multiple times each day to stimulate follicles, which are fluid-filled sacs that store eggs. They visit the doctor frequently for ultrasounds and blood work. Once the follicles reach a certain size, the eggs are retrieved, frozen and stored for later use. A single egg freezing cycle, including ultrasound monitoring and doctor supervision, can cost $4,500 to $8,000, though prices can vary and often don’t include the cost of the hormones and medications, said Dr. Mindy Christianson, medical director of the Johns Hopkins Fertility Center. Egg storage can cost more than $500 a year, she added.

Despite more women freezing their eggs in the last decade, fertility experts and endocrinologists don’t have clear success rates of live births from frozen eggs; they have only probabilities. And a majority of those women don’t go back to use their frozen eggs; a small study from 2017 found that only 6 percent of those who froze their eggs between 1999 and 2014 used them to get pregnant.

A study published this summer analyzed 15 years of data from 543 patients who froze their eggs at the NYU Langone Fertility Center and found that the overall chance of a live birth from frozen eggs was 39 percent. The younger a woman was, the greater a chance she had, in general, of a live birth. Even the A.S.R.M. concedes that egg freezing is neither a guarantee of fertility nor a one-size-fits-all solution.

The process is an intense and arduous journey for many women, riddled with uncertainty, according to stories shared with The New York Times. Among the hundreds of patients who described their experiences, many expressed joy and hope; others spoke of the crushing disappointment that can come with trying to do everything in their power to plan for parenthood, only to find it — as one woman put it — “illusionary.”

These are some of their stories.

Stories of success: ‘I feel really proud of myself for being patient.’

Today, the vast majority of women who freeze their eggs do it to preserve fertility: In 2020, only 6 percent of the almost 13,000 women who froze their eggs did so because they had to get chemotherapy or other potentially debilitating treatments.

Jenny Hayes Edwards was one of the first women in the country to preserve her eggs for nonmedical reasons. She first heard about the procedure in 2009 when she was 34 years old. At the time, she owned three restaurants in Colorado and barely had time to go on a date, let alone nurture a serious relationship, get married and have children. “I had zero money, we were in the middle of a recession and I was working 24 hours a day,” she said.

A friend, who was 40 at the time and going through a third, tough round of I.V.F., told Ms. Edwards she wished she had the option of egg freezing when she was younger. Ms. Edwards was persuaded.

She froze her unfertilized eggs in June 2010, before the A.S.R.M.’s official stamp of approval. She sold some jewelry, maxed out a credit card and used a portion of her inheritance to pay for the procedure. Exactly a decade later, in June 2020, the 45-year-old gave birth to a son using her frozen eggs — an outcome that the Centers for Disease Control and Prevention estimates occurs in less than 10 percent of women her age or older. Those eggs, she said, had helped her live with less urgency: She left her job, became a health coach and waited to find the right partner, meeting her husband in 2017.

“I approached everything differently knowing that those eggs were there,” she said. “I was calmer about my dating life, and I wasn’t panicked about my biological clock. I feel really proud of myself for being patient.”

Emily Gertsch woke up a few weeks after her 42nd birthday with what she called “intense panic” — the sudden sense that, despite wavering in her 30s, she now knew she wanted to be a mother. Ms. Gertsch lived in New York City at the time and embarked on three separate rounds of egg freezing, one right after the other, in the summer of 2020. She didn’t expect to enjoy the process, she said. But as she sat in the waiting room between seemingly endless blood tests, looking around at rows of other women, masked and spaced out six feet apart, Ms. Gertsch felt a sense of community — something she craved during the pandemic.

“I just savored every moment,” she said. Months after her third retrieval, she used donor sperm to fertilize eggs, creating an embryo — and in 2021, at the age of 43, she gave birth to her son.

They now live in Switzerland, where Ms. Gertsch, a single mother by choice, works at a pharmaceutical company. “I just appreciate it so much more, to know this is something I deliberately chose, this is exactly the life I wanted,” she said. “And I created that.”

Stories of disillusionment: ‘I genuinely have no idea where my eggs are.’

Jordan Marie Curry, a 35-year old talent acquisition director from Chicago, consulted with two doctors before she had surgery to remove fibroids from her uterus. They advised her to freeze her eggs in case the surgery compromised her ability to become pregnant. Her employer at the time paid for the annual storage fee for her frozen eggs, but once she left the company, she has paid $720 each year to keep them — even after she had a daughter in 2020, without needing to use them.

She struggled with whether or not to discard the eggs she froze; in an ideal world, she said, she would donate them to other Black women, but she wasn’t sure how to begin that process. And there were logistical hurdles to consider, including a fee associated with removing the eggs from storage.

The center where Ms. Curry’s eggs were frozen wasn’t the same place they were being stowed, and she had scant details about the storage facility. “I genuinely have no idea where my eggs are,” she said. “I think maybe Illinois?”

Maura Downs was 35 when she froze her eggs after an ectopic pregnancy left her with one ovary. She spent $20,000 on the procedures and medications, stopping at the hospital before work every two or three days to get her blood drawn.

“I thought it was going to give me this amazing insurance policy,” Ms. Downs said. She went through two rounds of egg freezing in total. Both left her with zero viable eggs.

Ms. Downs, 38, is now pregnant with a child she conceived without medical intervention, after trying for a year. “Knowing what I know now,” she said about freezing her eggs, “I regret it.”

Stories of hope: ‘I’m glad I’m not boxed in.’

For many women, egg freezing provides a sense of hope that is worth the physically intense process, the exorbitant costs and the unpredictable chances of success.

When Shira Moskowitz, a New York-based customer relations representative at a technology company, was 23 years old, in 2016, doctors removed one of her ovaries after discovering a cyst that had cut off blood flow to the organ. She knew that she eventually wanted to freeze the eggs from her remaining ovary; she started a savings account for the procedure.

She began the process about five years later: measuring doses of hormonal injections in her apartment with her roommate and running to the clinic for blood work every morning. In the end, her doctor retrieved 10 mature eggs to freeze, a number that is considered low. Still, Ms. Moskowitz, now 29, has no regrets.

“It sort of feels like this small insurance policy that I have in my back pocket, if I decide I want to have kids,” she said. “I’m glad I’m not boxed in.”

For Laura Kelly, a software engineer in Austin, the introduction of egg-freezing benefits to employees of Airbnb, where she worked, provided “the push” that she needed to go ahead with the procedure. She was 31 at the time and knew she wanted to get married and have children, but she was wary of rushing into a relationship with the wrong person. As a bisexual woman, she said, she knew that having eggs already frozen would be a step ahead if she wanted to conceive a child with another woman.

“Talking to women about it who I’ve dated, everyone expects it’s going to be a really extensive process,” she said about having children. “Having that first step done is nice — it feels like we have a lot of options, like part of it is going to be less strenuous.”

Evelyn Gosnell, a behavioral scientist from San Francisco, knew when she started her first egg-freezing cycle at age 32 that the process was not a guarantee. Still, when a doctor informed her that he had retrieved only seven eggs, she didn’t know that number was comparatively small (women under 38 who successfully conceive after freezing their eggs typically retrieve 10 to 20 per cycle). “My doctor didn’t say that seven eggs wasn’t great — I certainly had no idea that seven eggs were not sufficient,” she said.

Ms. Gosnell froze her eggs again at 36 and once more at 38, in grueling cycles that brought her cumulative total to 30 eggs. Even her gynecologist was impressed at that number, Ms. Gosnell said, making the possibility of one of those eggs turning into a baby seem like “a done deal,” she said.

But not all frozen eggs survive thawing. Not all merge properly with sperm to form early stage embryos, called blastocysts; and not all blastocysts are considered viable. After paying $45,000 for egg freezing and an additional $15,000 to have her eggs thawed and fertilized, Ms. Gosnell was in a meeting at her office when she received an email from the fertility clinic, informing her that the single blastocyst she had created was abnormal. She would not conceive a child. The blastocyst, the email said, would have been a girl.

Ms. Gosnell, now 41, recently underwent two rounds of I.V.F., leading to two chromosomally normal embryos. These days, she said, she oscillates between optimism and realism, while trying to give her body its best shot at carrying a child. She gets acupuncture, she listens to podcasts about egg freezing, she reads books about fertility.

“You just want to know that you did your part, you did what you could do,” she said. “And then, you just have to let go.”