Medical & Laboratory Director, Columbia University Medical Center
Medical Director, Generation Next Fertility
One major weakness of egg freezing is that there is no way to test the quality of eggs on their own. So you won’t really know the potential of what you froze until you decide to use your eggs. In contrast, embryos must overcome many crucial hurdles that will give your doctor a much better sense of their quality, and their likelihood to result in a baby later. This has led to a healthy debate as to whether, when preserving fertility, freezing eggs is best, or freezing embryos is better.
There are compelling arguments on both sides that you’ll want to understand before making this very personal decision, and we’ll walk you through them.
When a woman freezes eggs she is “flying blind” when it comes to her visibility into whether those eggs can actually lead to a live birth. That’s because there’s no way to test eggs on their own to determine their quality, and the following crucial hurdles remain:
This can lead to a problematic situation where a woman’s eggs don’t perform as well as she would have liked but, by the time she realizes this, her egg quality has declined further -- with perfect information she may have chosen to freeze more eggs up front, but she didn’t find out until it was too late.
Conversely, women who freeze their embryos have much greater insight into whether what they’ve elected to freeze will lead to a live birth. That’s because turning eggs into embryos requires that they be successfully fertilized, and that those embryos survive until a point when they can be frozen, which is usually blastocyst stage (around the fifth day of development). Embryos are graded at each point in their development, which reflects an embryologist’s opinion of whether they are high quality or not. Finally, with embryos you have the option to run a genetic screening test on them with hopes of predicting more accurately whether they’re likely to become healthy babies.
Below we show what an egg freezer knows. We also include what an embryo freezer knows (with two scenarios as examples).
Here, the woman who froze her eggs knows that she has stored 15 eggs. She knows nothing else.
Alternatively, the woman froze embryos has a more enlightened point of view on those 15 eggs. In scenario #1, the embryo freezer may be comforted with the result and choose to not undergo another cycle. Risk still remains that her three embryos will not lead to a live birth, but many unknowns have been addressed. On the other hand, if this woman ends up in scenario #2, she’ll learn two things. First, her efforts won’t yield a child. So she may want to do another cycle. Second, she may pick up on an important clue about her laboratory’s ability to work with her eggs (very few fertilized and none become embryos). That may inform her decision of whether to go to a different clinic. So, as you can see, women who elect to freeze embryos have a tremendous information advantage.
Embryos are typically more robust than eggs and thus are easier to freeze and thaw. This is demonstrated by the fact that excellent laboratories manage to successfully thaw 99% of frozen blastocyst embryos, and minimally competent labs can thaw 90% of them.
Freezing embryos is extremely common. In fact, the majority of IVF transfers in the US now use embryos that have been frozen. So it’s likely that your clinic has a proven track record of freezing and thawing embryos (though you should verify this).
Historically, freezing eggs was much more of a gamble. This has started to change with the advent of better freezing technology called vitrification. Now, in excellent labs, they expect 90% of the eggs that they freeze to survive a thaw, and in minimally competent lab it’s closer to 80%.
Some labs are excellent at freezing and thawing eggs. As you can see from one lab’s data below, they show no difference in results when doing IVF with fresh eggs or frozen eggs. Often, the clinics with the best results publish their track record.
Yet rarely is the rest of the field anywhere near as competent. In this case, most clinics have minimal experience freezing and thawing eggs, let alone enough of a proven track record to publish their performance. Thus, it would be a mistake to automatically presume your clinic’s laboratory achieves similar results.
So, it is generally accepted that there’s a higher chance of embryos surviving a thaw than eggs, but it’s crucial for you to investigate what the capabilities are of your lab so you can understand if the added risks are minimal.
The down-the-road, non-medical implications are where the arguments for egg freezing really grow strong.
First and most obviously: freezing eggs will allow you the flexibility to choose who the genetic father of your children will be. This could be a future partner or a donor. Since life flexibility is a big reason people think about freezing eggs in the first place, this is clearly a huge draw.
Legally, embryos can also be more difficult.
When making embryos, you have the choice to use a sperm donor either anonymously from a sperm bank or someone you know, or a current romantic partner like a boyfriend or husband.
Using a sperm donor from a sperm bank gives women legal authority over the embryos. It’s when a partner is used that things can get very complicated -- there are plenty of legal cases that have cropped up in different states recently in which a woman has wanted to use the frozen embryos, but the male partner has successfully blocked her from doing so. If you’re using a romantic partner or even a known donor like a friend, you’ll definitely want to meet with an attorney specializing in reproductive technology beforehand so that you can ensure you’ll have full rights to the embryos.
Finally, there’s a legal unknown, as congress has continued to propose legislation that would say life begins at conception. It’s unclear what the implications would be for existing embryos, but it could make it harder to figure out what to do with them if you don’t ultimately end up wanting to use them.
Freezing embryos means you will spend more money up front. At minimum, you’ll need to pay the lab fees for fertilizing and growing the embryos, which is $3,000 - $8,000. You might opt to do further add-ons, like genetic screening to test the viability of the embryos, which would add another immediate $5,000. Finally, if you’re using donor sperm, you’ll end up paying about $1,000.
If you never end up needing to use your embryos, you’ll still have paid for these extra expenses. Whereas egg freezers who never use their eggs will have avoided these costs.
Though it might seem premature to think about what you would do with your eggs or embryos if you decide you don’t want to use them, it’s probably a good idea to give it some thought up front.
For dissolution of either eggs or embryos, there are typically a few options one can take: discarding them, donating them to research, or donating them to another person who wants to conceive.
Because storage costs really add up over time, especially if eggs or embryos are left at a clinic rather than an offsite cryobank, it makes sense to give this at least a little thought up front. If you never need to use them, would you personally have an ethical issue discarding eggs or embryos? Would one be more difficult for you?
We often speak with patients who are surprised at how difficult this decision is, particularly when they’ve decided to make embryos.
Though it will save you money to move eggs or embryos to a cryobank, at some point, if you don’t use them, you’ll probably be sick of paying annual storage fees. So thinking about dissolution up front is a good idea.
You might be reading this and thinking, the whole reason I want to freeze my eggs is because I’m single, or not sure I want to become a parent with my current partner -- isn’t the whole point of this to take the pressure off of me to pick a genetic father to my children?
That’s completely fair. We bring this up because it’s a decision point many women go through, particularly if they are freezing after age 35 when there’s less clarity as to whether their eggs will work out for them.
There’s also a middle ground, where some women choose to freeze some embryos, and some eggs -- this usually, but not always, means they are doing multiple cycles.
The women who choose to get a sperm donor and freeze embryos instead of eggs are essentially making a few key decisions about their priorities. Here are a few of the most common that we hear: