It’s a little tricky to get a handle on egg freezing success rates. Many women don’t use their eggs for many years after they’re frozen, and some don’t use them at all—making data a bit more difficult to compile.
For example, most of the statistics available for egg freezing success rates now are from eggs frozen when the procedure was much newer, and most labs were using the older, less effective “slow freezing” technique. As we’ve discussed before, the new form of freezing, called vitrification, is significantly more effective; studies demonstrate that 90–95% of eggs frozen using vitrification survive the freezing and thawing process (compared to just 61% of slow-frozen eggs). And here at Extend Fertility, we’re using an even more effective method of vitrification called Cryotec that has a near 100% egg survival rate. So the egg freezing success rates compiled from slow-frozen eggs are not reflective of the advances in egg freezing technology.
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Another example: the primary “success metric” reported by SART, the leading clearinghouse for data on in vitro fertilization (IVF) success rates, is live birth rates from IVF and donor egg procedures. That’s great information to know for those who want to get pregnant right away. But for those who are trying to ensure a chance at pregnancy a few years down the line, SART has little to offer: they report how many “oocyte banking” cycles each clinic performed each year, and not much else. (That’s why Extend Fertility can’t be found in SART’s database—the information they’re looking for doesn’t correspond with what we do here.) So we have to look elsewhere for egg freezing success rates.
Success rates for frozen eggs vs. “fresh” eggs
One of the most comprehensive studies that can help us understand egg freezing success rates was published in the journal Human Reproduction in 2010, entitled “Use of cryo-banked oocytes in an ovum donation programme: a prospective, randomized, controlled, clinical trial.” In short, this study examined the success rates of 600 women undergoing in vitro fertilization with donor eggs from young, healthy women. Half the group was randomly assigned to use frozen and thawed eggs, and half was randomly assigned to use “fresh” (recently retrieved) eggs. In the end, the researchers found no significant difference in pregnancy rates between the two groups, indicating that freezing eggs and thawing them for use later has no detrimental effect on success rates. They concluded that their study “confirmed the effectiveness of oocyte cryo-storage.”
What that means in terms of egg freezing success rates: your eggs will have the same chance of becoming a baby when you freeze them and use them later as they would if you fertilized them and used them in an IVF cycle now. For most women, that chance is determined by their age at the time of treatment (or freezing).
The effect of age on egg freezing success rates
Here, we can look back to our friends at SART for help in determining egg freezing success rates. In their 2010 Clinic Report National Summary, SART reported IVF success rates (in terms of the percentage of IVF cycles that resulted in live birth) by age: 41.5% for women under 35, 31.9% for women 35–37, 22.1% for women 38–40, 12.4% for women 41–42, 5% for women 43–44, and just 1% for women 45 and older. The same document also reported that live birth rates for egg donor cycles—which typically use eggs from young, healthy women in their 20s—are close to 50%, regardless of the age of the woman carrying the baby.
This gives us an idea of the chance of pregnancy through IVF at different maternal ages. Since, as we learned above, freezing and thawing eggs doesn’t affect how likely they are to result in pregnancy, we can think about it like this: if a 35-year-old woman has a 41.5% chance of getting pregnant in an IVF cycle using her own eggs, she’ll have about the same chance—41.5%—of getting pregnant using those same eggs if she freezes them at 35 and uses them later. (In fact, women who freeze their eggs may have even better chances at pregnancy than a typical IVF patient, because most women undergoing IVF already have an underlying problem with fertility that healthy egg freezers might not have.) This gives us one way to approximate egg freezing success rates.
This information also gives us another important piece of info about egg freezing success rates: the likelihood of success with any fertility treatment varies depending on the age of the egg more than the age of the mother at the time of pregnancy. Young, healthy eggs can give a mother of “advanced maternal age” a good chance at pregnancy, whether those eggs are from a donor—or whether she acts as her own “donor” by freezing her eggs.
How many eggs should I freeze?
The second factor in egg freezing success rates is how many eggs a woman is able to freeze. As our chief clinical officer Dr. Joshua Klein writes in his whitepaper “Egg Freezing and the Biological Clock”:
Just like with IVF, when it comes to egg freezing, we know that producing and freezing a larger number of eggs is directly associated with increased egg freezing success rates. In one of the largest published studies analyzing outcomes from almost 1500 women who froze their eggs at age 35 or younger, the chance of live birth increased from 15% for women who froze just 5 eggs, to 61% for women who froze 10 eggs, and 85% for women who froze 15 or more eggs.
New research on egg freezing success rates
Just last month, a study was published that gives us an excellent new tool for predicting egg freezing success rates: a model that combines the woman’s age at the time of freezing with how many eggs she’s frozen to determine her chance of a healthy pregnancy. Based on the cycle data of 520 healthy, fertile women undergoing treatment at Brigham and Women’s in Boston, the study, published in Human Reproduction, predicts that women under 35 who freeze 10–20 eggs have between a 70 and 90% chance of at least one live birth later on.
Table courtesy of Human Reproduction.
This model is groundbreaking because it is the first to predict egg freezing success rates based on maternal age by individual year—important, since doctors know that fertility changes drastically throughout a woman’s 30s—and to incorporate the chance of creating a genetically healthy embryo, which decreases as a woman gets older. (Learn more about egg quality.)
The younger, the better
One thing that all of these models, predictions, and studies point to is that the younger a woman is when she freezes her eggs, the better her chances will be at success later on. This is both because younger women’s eggs are less likely to create genetically abnormal embryos (egg quality) and because younger women are more likely to respond better to egg freezing treatment and produce more eggs in one cycle, and more eggs means higher egg freezing success rates.
The second thing we know is that these egg freezing success rates are just general rules. The only way to predict your personal fertility health is by getting the facts about your egg quality and quantity.