Egg Freezing

At this point it might be beaten into your head that women’s fertility potential declines with age. That’s true, but here’s the problem: we have surprisingly little credible data on how quickly fertility dissipates for women in the general population.

This makes it incredibly difficult to use age to predict with any accuracy whether you’re likely to need IVF, especially during a woman’s thirties and early forties.

Women who are considering egg freezing are often shown charts like the one below depicting an age-related fertility decline:

The data in that chart, the standard used by ACOG and ASRM, does not meet our internal bar of what we’d show you on this site and we think you should view it (and others like it) with caution. Here’s why:

• The chart shows how many children happened to be born to women at each of these ages. This is a poor proxy for ability to conceive because it does not account for whether couples were even trying to conceive. As you’ll see in the next bullet, that’s especially important given when this data was collected
  
  
• Much of the data is sourced from the 1600’s and 1700s. The average life expectancy at this time was 30 - 35.
  
  
• Given this, it’s highly possible women in their 30’s and 40’s produced so few children (as indicated in the chart) because many were nearing the end of their lives or already dead.
  
  
• Old data is also problematic because it means we are studying a population entirely dissimilar to modern-day women (as exemplified by the 2x shorter life expectancy)
  
  
• The methods for data collection in the 1600s and 1700s were crude and the computational tools to isolate out variables did not exist.
  This is all to say that if you’re 33 today, and don’t see yourself having kids before 38, we don’t have any good data to show you about how much harder it will be for you to get pregnant at that point.
  
  

Infertile Population

What we do have is a lot of data showing that for women who needed to use IVF to have babies, their success rates declined significantly with age. This data tells us why doing IVF with younger eggs is helpful, but there is no proof it reflects the patterns of the general population trying to conceive.

In short, age, on its own, isn’t a perfect predictor of whether you’ll need to use medical assistance at a given point in time to build your family, but it does show us that if you become infertile, treatments become much less effective with age.

There are a few tests that are generally marketed to women as “fertility predictors” or “egg counters” that will reveal the secrets of their ovarian reserves. The most frequently mentioned is the AMH, followed by the FSH. These tests can be very helpful in predicting a woman’s response to fertility medications, if those medications are needed (which generally happens after a couple has tried to conceive for a year). What they do not give us is a prediction of baseline fertility, or how likely it is that you will struggle or get pregnant easily if you try at some point in the future.

Below is data from one study showing that women of varying AMH levels conceived at a similar rate and after a similar number of attempts.

The same appears true of FSH and time to conception:

While this study suffers from two weaknesses (low sample size and an endpoint that is not “live birth”), the data is persuasive.

Women are often spurred into egg freezing based on learning they have a low, or a low-end-of-normal-range AMH. What AMH will give you is insight into how an egg freezing cycle will go if you choose to go that route -- if you have a low AMH, expect to collect relatively few eggs, and feel the need to do several cycles to collect an egg number you feel confident in.