Freezing eggs for later: the number that is almost never quoted
Most women who freeze their eggs never use them.
Egg freezing is sold as an insurance policy. The clearest way to see what it actually delivers is to follow a group of women long enough to find out what happened.
| Cohort | Women who froze | Who came back to use them |
|---|---|---|
| Spain, 2007 to 2015 | 1,468 | 137 (9.3%) |
| Spain, 2007 to 2018 | 5,289 | 641 (12.1%) |
| US academic centre, 2006 to 2020 | 921 | 68 (7.4%) |
| US, first retrievals 2005 to 2009, followed 10 to 15 years | 231 | 88 (38.1%) |
The first three figures are not lifetime rates, because those groups include many women who froze recently. The last one is the only cohort with enough elapsed time to approach a final answer, and even there: after 10 to 15 years, 47.2% of the women still had their eggs sitting in storage, and only 38.1% had ever thawed them. The mean age of the women who eventually discarded their eggs was 47.4 years.
Among those who did come back, the live birth rate clusters around one in three, though each study uses a slightly different denominator: 33.8% per patient with a final outcome (27 of 80) in that long-followed cohort, 32.4% per patient who returned and thawed in another, 39% per patient who thawed in a fifteen-year series. It rises above 50% for women who froze under 38 or who thawed 20 or more mature eggs.
Two cohorts let you work something out. In the long-followed US group, 27 of the 231 women who froze went on to have a baby, which is about one in nine, after 10 to 15 years and with about half the women still leaving their eggs in storage. In the larger Spanish group, forty babies came from 1,468 women who froze, which is about one in thirty-seven, in a cohort where many women had not yet reached the age at which they would return. Neither figure is a published rate, and the gap between them is mostly a difference in how much time had passed.
If a clinic quotes you a success figure, ask which denominator it uses.
How many eggs. In the 137 women from that Spanish cohort who came back and thawed, cumulative live birth per egg used:
| Age at freezing | At 5 eggs | At 8 eggs | Plateau |
|---|---|---|---|
| 35 and under | 15.4% (95% CI −4.2 to 35.0) | 40.8% (95% CI 13.2 to 68.4) | 85.2%, the rise slowing over 10 to 15 eggs |
| 36 and over | 5.1% (95% CI −0.6 to 10.7) | 19.9% (95% CI 8.7 to 31.1) | 35.6%, reached at 11 eggs |
Look at the five-egg column before anything else. Both of those intervals run below zero, which means five eggs is compatible with no live birth at all. That is the cell a woman deciding whether one cycle is enough should read first.
The authors concluded that at least 8-10 metaphase II oocytes are necessary to achieve reasonable success
, and that women motivated only by wanting to postpone childbearing should be encouraged to come younger.
One more figure from that cohort keeps the rest honest: of the 1,468 women who froze eggs, 137 came back, and forty babies were born from the whole group.
There are not yet sufficient data to recommend oocyte cryopreservation for the sole purpose of circumventing reproductive aging in healthy women.
The current fertility ethics opinion calls the procedure ethically permissible and adds that because it
is new and evolving, it is essential that those considering using it be informed about the uncertainties regarding its efficacy and long-term effects.It also states that
Centers need to be specific about the extent of their experience with planned OC and their own results, and explicitly disapproves of practices paying marketing firms per patient recruited.
- "How many mature eggs are we aiming for, and how many cycles will that take at my age?"
- "What is your centre's live birth rate for women who have come back and thawed?"
- "What does storage cost per year, and for how long?"