They started cleaning up the counter, disposing of the needles and plastic wrappers. Over the next thirty-five hours, Remy’s follicles would finish maturing all the eggs that had been developing since she started the hormone shots.
“Now what?” said Leah.
Remy, already on her way back to the sofa, tightening her ponytail, replied: “Now we finish watching Crazy Rich Asians.”
—
So far, egg freezing had been straightforward for Remy. Yes, injecting herself with fertility hormones was complicated, but watching her going through the process up to this point showed me that the experience itself didn’t have to be. She made it look doable. That she was a doctor and so comfortable with the shots, the blood work, and all the acronyms certainly helped—and it made our situations less comparable. But it was also her attitude, how confident and self-assured she’d been since the moment she decided to freeze. She’d advocated for herself and been proactive every step of the way. Her optimism was a welcome breath of fresh air. I envied her certainty—and her two healthy ovaries. When I met Remy, I’d already decided to freeze my eggs. I hadn’t changed my mind, but I was stalling. As much as I wanted my egg freezing experience to look like Remy’s and that of other women I’d met who had done it, I knew it probably wouldn’t. The stakes were different for me. Higher. I had one ovary; if anything went wrong, I had much more to lose. On the other hand, what if some other bizarre thing happened—another ruptured cyst, another emergency surgery—and my ovary had to be taken out? If that happened, I would forever regret not freezing my eggs when I’d had the chance.
Checked Boxes and Longings
At five feet tall and just under 115 pounds, my mother doesn’t look like your typical U.S. Army colonel. She was commissioned into the Army in 1978; hers was the third class of ROTC college graduates to include women. My mother has been many things: high school valedictorian, state supreme court legal clerk, Girl Scout troop leader, battalion commander, mother of three, an ethics attorney for the Department of Justice. She has jumped out of airplanes; she’s prepared soldiers for immediate deployment after 9/11. She gardens and bakes cookies. Some mothers teach their daughters how to ski, or cook, or work a sewing machine. Mine taught me the military phonetic alphabet, how to hold a rifle, and the most efficient way to lick cookie batter off the beaters of a mixer. My mother was a trailblazer who also liked to mow the lawn on hot summer days and tuck her daughters into bed, reading us library books out loud. She maxed out on the military physical training test every year—push-ups, pull-ups, running a fast mile—and loved a good manicure. She didn’t change her last name when she married, not because it was post-1960s and she felt like being radical but because her parents had always told her: Don’t do something just because everyone else is doing it.
The world my mother became pregnant in is nothing like the world I live in. But I was raised to do what I wanted to do, and I grew up believing I had permission to live as fully as my mother did. Women of my generation were promised by a liberated society that we could do and be anything we wanted. It’s a promise we are not apt to forget. We are taught to never give up, to always be striving, to pursue happy endings—whether by holding out for them or by manifesting them. This mindset is true in love and in the pursuit of motherhood, where discussions are rife with talk of miracles and perseverance. On the surface, anything seems possible. But when we dig deeper, we find we are following the same myths I’ve been focusing on: the illusion that any woman who tries hard enough can have whatever she dreams of, whenever she wants it, as long as she takes matters into her own hands.
It was starting to make more sense to me now why young women like me are quick to buy into the notion that when it comes to fertility, taking action is required if a woman is to maintain a sense of agency in her life. If the 1960s saw the rise of birth control and sexual liberation for women, the 2010s were the decade that freed women from thinking they have to settle, ushering in the second phase of trying to have it all. This was, after all, the time of Lean In and #girlboss and the possibility of the United States’ first female president. When I was a girl, the message was: It doesn’t matter that you’re female! Go be whatever you want to be. Now there’s a backlash of sorts, with biology and culture telling us otherwise, that being a mother is a not-to-be-missed experience, that being a wife is a status upgrade because we live in a world that regards romantic partnership as the sine qua non of content adulthood.
And so it’s not difficult to see how women being given the potential to pause their biological clocks—or at least muffle the ticking—is as potent a possibility as it is. In the context of social pressures and expectations, egg freezing is an easy sell. At first glance, it seems like an ideal technological solution to a long-standing human conundrum: How can women postpone having children until the exact time in their lives that makes the most sense for them?
I recalled Remy telling me about how, in her twenties, she had approached certain aspects of life as if they were boxes to check off. Namely, becoming a doctor, but also dating. She had approached romantic relationships with the same checklist mentality with which she approached her career, and she expected return on investment in both. But as she entered her thirties, she realized that despite her best efforts—sincere, time- and energy-consuming efforts—the neat and tidy boxes of some of the most important parts of her life were, well, not so neat and tidy after all. “Turns out that’s not really how life works,” Remy told me. “A lot of the life components that I viewed as checked boxes ended up being the least stable. I obviously didn’t pick the right partner, either time. What ended up being the most stable was my career.”
I remember when the checked boxes I envisioned for myself began to shift. It was the day I moved back to the United States from Sri Lanka and was given a warning. “Your passport is full,” the officious customs agent had said. It was a Friday afternoon in July; the immigration lines at Washington Dulles International airport were hours long. The agent glanced at my short hair and thin cheeks, then back down at a picture of me taken dozens of countries and a lifetime ago. “You are not permitted to leave the U.S. again until you get a new passport.”
“That’s fine,” I replied, adjusting my heavy pack. I had been back in the States for seventeen minutes. “I’m not going anywhere for a while.” Every page in my passport was covered with stamps and visas. I had lived on four continents, sometimes for years at a time, and had just returned from a yearlong Fulbright scholarship. I loved traveling and was confident it would remain a major fixture in my life. But I was beginning to yearn for roots, the kind that would make staying in one place for a while the adventure rather than the default. I was still young, but I was also making plans—the kind I wanted my boyfriend at the time, whom I’d been living halfway around the world from for the past year, to be a part of. My worn passport was ready for a rest, and so was I.
Several years later, I can still feel the sweat underneath the straps of my backpack, the buzz of activity in the airport terminal. I was in my early twenties then, and the concept of marriage and babies seemed abstract, even though certain events had caused me to consider the baby part. But I was very much in love, and I remember how arriving back in the States coincided with a strong feeling of self-imposed pressure to put my relationship and romantic future ahead of my nascent career ambitions for a while. Then, less than a week after I returned home, my boyfriend broke up with me—later I’d come to understand his reasons, but at the time it felt so out-of-nowhere that it almost didn’t seem real—and the aftershocks of our painful breakup pushed all thoughts of roots and future children out of my mind.
Now life was different, especially in the relationship department: I was falling more in love with Ben. We’d experienced a lot together since we started dating. Christmas with my family, Thanksgiving with his. We’d been each other’s date at our best friends’ weddings, we’d shown each other our college campuses. His comments about fatherhood had moved me, and the more time I spent with him, the more clearly I could picture him as a father—putting together the crib, doing dozens of Target runs, him getting out of bed at 2 a.m. instead of me when the baby cried. Every now and then I’d feel a pang, a sort of longing ache, at the thought of being pregnant with our daughter or son.
I had been rethinking my exuberant Yes, let’s freeze my eggs! declaration I’d made at the fertility clinic. I’d had the preliminary assessment, done the blood work. Next up was deciding when to attend the mandatory egg freezing orientation session at the clinic, where I’d learn about injecting the medications. Yes, I’d been putting off scheduling this next appointment, but I still had a lot to look into. Among the rabbit holes I had yet to fully immerse myself in was the efficacy. It was time to find out how successful egg freezing actually was.
Does Egg Freezing Work?
I took a deep dive into what’s known about the number of women freezing their eggs and egg freezing’s success rates. And what I found was conflicting statistics, cherry-picked figures, and just straight-up impossible numbers. I noticed that articles and studies discussing egg freezing’s popularity relied exclusively on data from the Society for Assisted Reproductive Technology (SART), so I reached out to them, hoping someone could help me whittle down my growing list of questions. SART’s president at the time sent me spreadsheets of raw data and explained several figures to me over a few phone calls and emails. Later, other folks at SART provided me with updated statistics and helped me arrive at clearer numbers. I mentioned them in chapter 1, but I’ll unpack them here.
Between 2009 and 2022, nearly 115,000 healthy women in the United States underwent egg freezing. In 2009, the number of healthy women choosing to freeze their eggs in the United States was 482; in 2022—the latest year for which official data is available, as of this writing—it was 22,967.[*3] That same year also saw a 73 percent increase in the number of egg freezing cycles from two years prior. And in terms of fertility preservation as a whole, I was surprised to learn that in 2021, 40 percent of all ART cycles performed in the United States were cycles in which all resulting eggs or embryos were frozen for future use. This is significant, considering that for nearly the whole time ART has been around, the main type of ART has overwhelmingly been IVF—that is, women attempting to get pregnant now, not at some unknown future date. This marked rise in fertility preservation is a growth trend that is all but certain to continue, and likely increase, in coming years.
Okay, so, egg freezing has grown sharply and is continuing to soar. But what’s been happening with all those thousands of frozen eggs? And more importantly, what happens when they’re thawed? Turns out that it’s difficult to determine, with any real certainty, how well egg freezing works. When we talk about its success rates, the conversation gets convoluted fast. It took me weeks of focused research to figure out exactly what we do know and what we don’t, and why. To get to the bottom of the efficacy of the process, I needed to understand what data the procedure’s success rates are based on. After more digging, I learned the bad news: Reliable data is paltry, mostly because it’s proved difficult to compile the kind of information from which helpful conclusions can be extrapolated.
There are a few reasons for this. The first has to do with the technology. The bit of good news I found reaffirmed that the science behind egg freezing has come a long way since it was developed roughly thirty years ago, particularly in terms of more dependable thawing methods and more effective ovary-stimulating medications. Vitrification—the science involved in the actual freezing of eggs—was, as I’ve mentioned, a game changer for the procedure. The downside of this otherwise optimistic news is that a lot of the egg freezing data available today was compiled from non-vitrified eggs, when clinics were using the less effective slow-freezing technique, which means it’s not reflective of the advances in egg freezing technology used today. This has muddied the waters and makes comparing “what was” to “what may be” in terms of frozen eggs’ pregnancy potential difficult to predict. What’s more, many of the studies done early on focused on younger women who froze their eggs due to cancer diagnoses. That’s a very different demographic compared to older women without medical conditions who are pursuing fertility preservation, which characterizes most egg freezers today.
A second, significant issue is that we simply don’t have reliable data—and won’t for some time. One obvious way to measure whether or not egg freezing works, I figured, would be to look at how many healthy babies were born from those eggs that were used. Problem is, it’s just not known how many babies worldwide have been delivered from a woman’s own frozen eggs. By most estimates, it’s in the low thousands—a number sure to increase over time. I had assumed egg freezing’s popularity could be attributed to the fact that it worked—and that there were firm numbers to prove it. But there aren’t, simply because most women who have frozen their eggs haven’t gone back to use them.
A small but important study published in the scientific journal Human Reproduction in March 2017 found that only 6 percent of those who froze their eggs between 1999 and 2014 had used them to try to become pregnant. A 2023 Journal of Clinical Medicine study—the first to review the worldwide literature on outcomes of egg thaw cycles following social egg freezing—showed that “the average return rate is low, around 12 percent.” Other sources have concluded similarly, finding that fewer than 15 percent of American women who have frozen their eggs have thawed them. The reasons vary. Some women never find a suitable partner, or else they end up conceiving through sex; others are postponing returning to their frozen eggs in case of a divorce or in hopes of having a second or third child down the line. In these cases, the eggs represent a contingency plan that these women—so far—haven’t chosen to use. This illuminates a few crucial facts often left out of conversations about egg freezing. One, how few women have tried to get pregnant using their frozen eggs. Two, that many women don’t attempt to use their eggs for several years after freezing them. And three, that many women won’t end up using them at all—but it will be years until we can say that with any degree of certainty.
A common mistake when talking about egg freezing’s live-birth rates is to point to a single statistic and call it a day. I know this to be true because it’s what I did before I got into the weeds with the numbers. A few years ago, there was an oft-discussed scary statistic from ASRM referenced by many journalists and media outlets writing about egg freezing. I latched on to this stat myself in one of the first articles I published on the topic—and learned just how easy it is to misinterpret egg freezing data. At the time, ASRM’s stat put egg freezing success rates at between 2 and 12 percent—disastrous! But that statistic refers to live-birth rates per egg retrieved, using the older freezing methods. Live-birth rates from eggs frozen using vitrification, as I’ll get into in a moment, are more promising. But the main reason that statistic is misleading is that it’s the live-birth rate per egg—and virtually no one freezes just one egg.
Once I understood why there is so little data on vitrified eggs from women freezing for non-medical reasons and why studies reporting outcomes in women returning to use their frozen eggs are scarce, I turned to evidence from other contexts. Much of what we do currently know about egg freezing, I found out, relies on egg freezing cycles for egg donation or for medical reasons (more on egg donors in chapter 10) as well as statistics extrapolated from IVF data. When doctors talk about egg freezing success rates, they tend to compare the procedure to IVF or egg donation. Both of these ART procedures involve ovarian stimulation, as egg freezing does, but they are not the same, and chiefly are used by different subsets of patients. IVF is often done with fresh—that is, recently retrieved—eggs; egg donation often uses frozen eggs from women in their early twenties. And, as a Time article noted, “While anecdotal evidence suggests egg freezing is comparable to IVF because frozen eggs behave like fresh ones, IVF itself is hardly foolproof—even in women under thirty-five, the majority of cycles don’t result in a live birth. But because IVF is such a common procedure, women are often reassured when they hear the comparison.” The good news is that the smattering of existing findings indicates similar pregnancy rates whether using fresh or frozen eggs for IVF and that freezing eggs and thawing them for use later has no detrimental effect on a woman’s pregnancy potential. So, while these are extrapolated conclusions, this is encouraging information for women hoping to become pregnant with frozen eggs down the line.
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In an effort to help fill the void, some fertility clinics have taken it upon themselves to compile and publicize their own statistics. NYU Langone Fertility Center, one of the longest-standing clinics in the field, has completed more than three thousand egg freezing cycles since their egg freezing program began in 2004. In 2022, a study published in the journal Fertility and Sterility analyzed fifteen years of data from 543 patients who froze their eggs at NYU Langone between 2002 and 2020.[*4] The study showed that 74 percent of eggs survived the thawing process and nearly 70 percent of those surviving eggs were successfully fertilized. It also found that the overall chance of a live birth from frozen eggs was 39 percent. The average age when women froze eggs was thirty-eight, and on average they waited four years to return to the clinic to use them. Among women who were younger than thirty-eight when they froze their eggs, the live-birth rate was 51 percent. It rose to 70 percent if women younger than thirty-eight also thawed twenty or more eggs. So the study’s conclusion is no surprise: The younger a woman was when she froze her eggs, the greater a chance she had of a live birth.
At first glance, these live-birth rates from frozen eggs may not seem very encouraging. The pregnancy rate is not as good as a lot of women think it will be. But it’s crucial to understand that the current data on live-birth rates using frozen eggs doesn’t offer a clear picture on how well egg freezing works because the numbers aren’t there. As frustrating as that may be, it’s the reality. We simply do not have robust data yet on unused frozen eggs. Unthawed eggs, then, do not represent any kind of failure; they can only be characterized as such if they prove unviable when they are unfrozen.
Another takeaway from the NYU Langone study and others like it is that their data reaffirms what fertility doctors have talked about anecdotally for years now: that many women who freeze their eggs do not get pregnant because of the age at which they preserved them and/or because they did not preserve enough eggs. It’s the same quantity-and-quality idea from our egg discussion in chapter 2. Getting many high-quality oocytes is key with egg freezing, and younger women have a distinct advantage both because they produce more eggs and because a higher proportion of their eggs turn out to be good. Egg quality: Younger women’s oocytes are more likely to create chromosomally normal embryos. Egg quantity: Younger women are more likely to respond better to the hormone injections and thus have more oocytes extracted in a single cycle.
And the more eggs a woman successfully retrieves, the better. Why? Because not all eggs will become viable embryos. First of all, remember that usually not all extracted eggs are mature, and only mature eggs can be fertilized. Then, some eggs won’t survive the thawing process. And not all eggs that make it to the fertilization stage will merge properly with sperm to form early-stage embryos. Finally, not all fully developed embryos will be genetically normal. Using frozen eggs to have a successful pregnancy is a multistep process, with many eggs or embryos lost along the way; one egg frozen does not necessarily equal one child. Which brings us to attrition rates.
When a woman is ready to use her frozen eggs, IVF picks up where egg freezing left off. Here’s how it works. First the eggs are thawed. Then they are injected with sperm. The next day, an embryologist will assess which eggs were fertilized, and the fertilized eggs are left in a petri dish for five to seven days, with some developing from early-stage embryos into what are known as blastocysts.[*5] Some of the blastocysts will grow into viable, chromosomally normal embryos.[*6] One of these embryos is then transferred into the uterus, where the hope is that it attaches to the uterine wall and implants successfully.[*7] Fertility specialists sometimes describe the success rates of thawing eggs, fertilizing them into blastocysts, and transferring a resulting viable embryo to the uterus as resembling an inverted pyramid: You start with a certain number of eggs and lose some at every step.
Let’s say Alex freezes twenty-four mature, good eggs. Eighty to 90 percent will survive the thaw, meaning about twenty of the eggs will make it to the fertilization stage, which is when the eggs are injected with sperm. It’s about a 75 percent fertilization rate, so that’s fifteen fertilized eggs. These fertilized eggs are left to grow for a few days, becoming early-stage embryos that are graded on certain characteristics. Most will reach day three of growth—in Alex’s case, that leaves twelve early-stage embryos—and some will make it to day five of growth, at which point they become blastocysts. An embryo that reaches the blastocyst stage of development consists of two types of cells, those that will develop into fetal tissues and those that will develop into the placenta. Finally, with an approximately 40 percent blastocyst conversion rate—50 percent is considered excellent—Alex will end up with four to six chromosomally normal embryos. Each has a 55 to 65 percent chance of resulting in a live birth. If Alex is twenty-eight years old when her eggs are frozen, about three-fourths of her embryos will be normal. If she’s thirty-eight, half will. And if she’s forty-two, one-fourth of the embryos will be normal.[*8]
While there is no magic number for how many eggs a woman should freeze to feel confident about the procedure “working,” a 2021 Journal of Assisted Reproduction and Genetics article that summarized the existing evidence around social egg freezing found that, on average, twenty eggs are recommended to achieve a pregnancy, with the minimum number being eight to ten. And the 2023 Journal of Clinical Medicine study I mentioned emphasized quantity being a crucial factor, determining that “irrespective of age at freezing, a significantly high live birth rate was achieved when the number of eggs frozen per patient was 15 or more.”[*9]
Two researchers at Brigham and Women’s Hospital and Harvard Medical School were among the first to try to assign probabilities to egg freezing based on a woman’s age and the number of eggs retrieved. Their analysis, published in April 2017 in Human Reproduction, uses a mathematical model based on data from more than five hundred healthy women in their twenties or thirties who underwent IVF (because of their male partners’ fertility issues) without freezing their eggs to extrapolate to women who elect to undergo IVF with frozen eggs. The study predicts that patients under thirty-five who froze ten to twenty eggs have between a 70 and 90 percent chance of at least one live birth later on. The most oft-cited favorable stat from their predictive model—note the word “predictive”; the study wasn’t based on actual births from egg freezers—indicated that a thirty-six-year-old woman who freezes ten eggs has a 60 percent chance of producing a live birth with one of those eggs. That’s pretty good. What’s really exciting, though, is that their study offers one of the best new tools for predicting egg freezing success rates, which, as we’ve seen, are difficult to parse. A calculator based on their work can be found online; SART, CDC, and a few fertility clinics also have publicly available calculators that women can use when trying to assess their individual chances of having a child using their frozen eggs.
You can see how the varying percentages and patient-specific factors make it challenging for fertility doctors to thoroughly inform their patients. But the good ones try to, because they know how important it is for women to take into account the many steps involved in attempting to use their frozen eggs. Dr. Temeka Zore, a reproductive endocrinologist at Spring Fertility in San Francisco, is explicit about what is and is not known about egg freezing’s success rates when she counsels patients considering the procedure. At the initial consult appointment, she shows a slide describing the attrition rates associated with frozen eggs. She walks the patient through the embryo development stages and explains that of all the eggs a woman freezes, only one-quarter will become chromosomally normal embryos that are suitable to be implanted in her uterus.
“Egg freezing is not a guarantee,” Dr. Zore told me. “It provides you with greater options for the future, but no one can guarantee that egg freezing will lead to live births.” Other fertility doctors I spoke with echoed one of Dr. Zore’s major concerns: that most women undergoing egg freezing don’t end up with enough eggs on ice. “Many patients think that, as an example, freezing eight eggs means eight chances at a baby,” she said. “It doesn’t. Because not all of those eggs will make it to embryos. I think that needs to be well stated by physicians. We have to be very clear as a field about the data—about what happens after you freeze and thaw eggs.”
To the common question of “How many frozen eggs do I need?” responsible fertility clinics and doctors offer a range. The more eggs a woman has frozen, of course, the better the chances of selecting the best eggs that will then be used to make chromosomally normal embryos and lead to a successful pregnancy. This is why many women do more than one cycle to retrieve more eggs. Those aware of the importance of getting enough eggs—who’ve really sat with what “enough” means in this context—often undergo multiple cycles to retrieve more eggs. For these patients in particular, the total number of eggs frozen is the end point, their awareness of what happens if they try to use their frozen eggs a good deal less clear. Not their fault—clinics aren’t always forthcoming on that part of the process. And while most fertility doctors understand that age-specific success rates are highly dependent on the number of frozen eggs a woman banks, many don’t explain to patients the possible need for additional cycles. Hence why hearing about Dr. Zore’s straight talk with egg freezing patients was so refreshing. As her explanation made clearer than most fertility clinics ever do, the reality is, most frozen eggs will not result in a baby.
So: Until more women who froze their eggs return to use them, we won’t have reliable numbers to predict more accurate and, hopefully, higher success rates. In the meantime, we glean what we can from the small studies that have been conducted—particularly the more recent and relatively more robust ones, like the NYU Langone study, acknowledging the caveat that the varied factors make it difficult to apply the extrapolated data to the general population—as well as from patient-specific egg freezing predictive calculators.
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All in all, I found that the data surrounding egg freezing success rates is both encouraging—and not very. Here are my takeaways after analyzing the numbers and research:
