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We all know that younger women, as a whole, have an easier time getting pregnant and giving birth to healthy babies. But understanding why that’s the case is more complicated.
There are at least two different factors that make successful pregnancy trickier for older women:
Let’s take a look at the impact of each on successful pregnancy. Then we’ll ask the question: which matters more - the uterus or the egg?
A baby girl is born with 1 to 2 million egg cells. That egg supply steadily decreases, giving the average adolescent 400,000 eggs and the average 37-year old 25,000 eggs.
Eggs don’t just decrease in quantity; they also decrease in quality, for several reasons. First, your body tends to pick the best quality eggs for use first - when you’re in your teens, 20s and early 30s. By the time you get to your later 30s and 40s, the remaining eggs are less likely to be as high quality.
Additionally, when the egg cell matures in the ovaries during the part of your cycle prior to ovulation, it needs to divide several times. Older egg cells are more likely to divide abnormally, leaving the cell with the wrong number of chromosomes. The result is an egg that will not fertilize, or - even if it does fertilize - will not develop correctly and will not lead to a successful pregnancy or a healthy birth.
Who hasn’t felt that her body at 40+ just isn’t the same as it was at 20+? (There’s a reason why women who don’t want to share their age often respond to “How old are you?” with the facetious answer, “21.”)
Women who get pregnant after 35 are more likely to experience pregnancy complications such as:
Gestational diabetes
High blood pressure
Pre-eclampsia
Complications during childbirth, including prolonged labour, need for a Caesarian section, or stillbirth
Any of those complications can decrease the chances of a healthy pregnancy and birth.
Before we ask that question, maybe we should ask: Why does it matter which matters more? If you’re over 35, both your eggs and the rest of your body is over 35 - so who cares?
While you can’t change the age of your body (unless you’ve invented a time machine), when you’re using IVF you can potentially change the age of your eggs. This can be done either by using donor eggs from a younger woman, or by using your own eggs, if they were frozen when you were younger.
So, it makes sense to care about and to find out which matters more. Let’s take a look.
The UK’s HFEA (Human Fertilisation and Embryology Authority) presents some very telling numbers in their most recent report, using data from 2017.
The numbers tell about the live birth rate per embryo transferred (PET). For women using their own eggs, the birth rate steadily decreases, from 27-30% (depending on whether the eggs were fresh or frozen) for women under 35, to 2-4% for women over 44.
For women using donor eggs, however, the decrease is much less significant (where there even is a decrease). Birth rate per embryo transferred is 28-33% for women under 35 - not too different from the numbers for that age group who use their own eggs. But birth rate for women over 44 is 22-26%. What a significant difference from the 2-4% for women who use their own eggs!
Why is this the case?
Donor eggs are almost exclusively from women under the age of 35. When they use these younger eggs, even women in their mid-40s have a significant chance of having a successful pregnancy and birth. True, it’s still not as high as the success rate of those in their mid-30s, showing that the older body and uterus do have an impact, but it’s far higher than women who are using their own mid-40-year-old eggs, showing the much greater impact of the egg’s age.
Another support for the egg’s age having a greater influence than the body’s age is seen by difference in success rate between women using their own frozen vs. fresh eggs. For those under 35, the IVF success rate is comparable when using their own fresh eggs. All older age groups, however, have a higher success rate for frozen eggs. The eggs, frozen at a younger age, boost their chances of success.
The same boost is seen when performing IVF using embryos frozen at an earlier age.
No, we don’t know of any miraculous source that will make you 21 again (if that’s even what you want). Your body is stuck at the age that it’s at. Period.
But the numbers given by the HFEA point the way to a potential fountain of fertility. Using younger eggs - whether your own frozen eggs or a donor’s eggs - can give you a higher IVF success rate. Additionally, the earlier you freeze your eggs (especially if you freeze them before 35), the greater your chances of a successful IVF pregnancy and birth.
We wish you much success in your fertility choices and in having the family you want, when you want.
While right now we have no way of freezing the biological clock, modern technology has given us a type of “snooze button.”
Freezing of eggs and embryos, otherwise known as cryopreservation, preserves these fertility keys at the biological age they were when frozen. Since the major factor in viable pregnancy and birth is the age of the egg and not the age of woman carrying the baby, this is great news for those women whose biological clocks are sounding alerts.
If you’re thinking about going this route, the next big question to ask is: are you going to freeze your eggs or your embryos?
This is not a simple decision, with many questions to ask and factors to consider before you begin. Below follows an extensive list of factors to help you decide which path is right for you.
The initial stages of egg freezing and embryo freezing are the same. You’re given medications which increase your ovulation and get more eggs ready than usual. The eggs are then harvested from your ovaries (an intravaginal procedure done under sedation).
This is the last stop if you’re freezing your eggs. If you’re planning on freezing embryos, on the other hand, now is time to go ahead and make those eggs into embryos. To do so, of course, you’ll need sperm - from your partner or from a donor - to fertilize the egg. If the egg fertilizes, it will be frozen once it has multiplied and reached approximately 50-100 cells.
This brings us to the first major factor in deciding between freezing eggs and freezing embryos:
Yes, it may be obvious, but we’ll point it out anyway: you need sperm to create an embryo. If you have a partner that you’re sure you want to have children with at a later time, or if you’re planning on using donor sperm anyway, then there are no obstacles to creating and freezing embryos.
If you’re single and still hoping to find the right partner to raise a family with, freezing eggs may make more sense. All you need for that is one party - YOU.
Eggs are more fragile than embryos, as they are only one cell (not 100), and that one cell is mostly water. But while earlier methods of egg freezing often created issues when the egg was frozen or thawed, the vitrification (flash-freezing) process that has become common in the past few years has brought success rates of frozen eggs up to par with those of fresh eggs.
When you freeze embryos, you know exactly how many fertilized embryos - how many chances at a viable pregnancy - you’re preserving. When you freeze eggs, on the other hand, you don’t know how many of them will fertilize when thawed.
That said, creating each IVF embryo usually requires multiple eggs anyway. This sample chart shows 2 viable embryos developing from a group of 12 eggs that were retrieved (obviously an individual’s results may vary). Assuming you matched this chart, as long as you froze all 12 eggs, it would basically be equivalent (probability-wise) to freezing 2 embryos.
As we all know, a viable egg - and even a fertilized embryo - do not (unfortunately) guarantee a successful pregnancy and birth. But do you have a better chance at a live birth when you start with a frozen embryo - or with a frozen egg?
The UK’s HFEA (Human Fertilisation and Embryology Authority) reports the following birth rates for frozen embryos using a woman’s own eggs and partner’s sperm, based on age of woman at transfer:
Under 35 - 27%
35 - 37 - 26%
38 - 39 - 21%
40 - 42 - 15%
43 - 44 - 8%
45 and up - 4%
Since reliable methods of freezing eggs are a more recent development, we have less data on frozen eggs (and especially on women using their own frozen eggs) than on frozen embryos.
What we do have, according to the HFEA, is a birth rate for frozen donor eggs in 2016 that was around 30%. This is comparable (and maybe even a little better) than the above rates for frozen embryos, but it doesn’t divide the data by the age of the woman at transfer.
The average birth rate for women using their own frozen eggs was 18%, which is similar to the birth rate for frozen embryos for women who at transfer were approaching or after the age of 40.
The HFEA points out that a reason why the donor eggs led to more successful births was that they were in general frozen earlier - and we know that the age of the egg is one of the most critical components. Additionally, in order to donate eggs, women need to meet specific health criteria, which is not the case for women who freeze their own eggs - which results in the pool of donor eggs being overall “healthier.”
According to that, if you use your own young, healthy eggs, you would likely have better results than the average, potentially bringing it close to the rate for frozen donor eggs and frozen embryos.
A helpful tool in your decision may be the Brigham Women’s Hospital Egg Freezing Counseling Tool. It’s a research-backed calculator that predicts the likelihood of a live birth for women who choose to freeze their eggs and use them later. (Note: as per the disclaimer on the tool itself, while it is based on research, “This calculator is not externally validated, and as such, should be used with caution.”)
When you freeze embryos that were fertilized with a specific partner, in certain senses you’re locking yourself in. While you might be head over heels with your current partner, and convinced you’re going to build a family with him someday, life bears witness that relationships don’t always work out the way we plan.
Most consent forms for undergoing IVF and freezing embryos contain legal clauses that stipulate how ownership of the embryos will be divided if the relationship ends. That said, if the breakup is nasty, you might face legal hassles… if you even still want to use those embryos.
Egg freezing avoids all these issues. Your eggs are yours alone, to use if, when and how you want.
In practice, many women don’t end up using their frozen eggs and embryos, either because they conceived naturally, they decided not to have children, or they reached their ideal family size before using all the eggs/embryos. What happens to your genetic material once you decide you don’t need or want it anymore?
Many faiths consider an embryo a human life and have restrictions on how one can treat it, even if it is no longer needed. Aside from faith, it is not uncommon to feel uncomfortable about casually disposing of an embryo. Unfertilized eggs, on the other hand, are much simpler to dispose of, both emotionally and ethically.
An unexpected insight comes from Briallen Hopper, who found that having embryos (from donor sperm) safely frozen actually diminished her possibilities for romantic love.
In her early 40s, Briallen wants to have children - but men who want to have children are starting to rule her out as a potential partner. Her chances of conceiving naturally are getting significantly lower - and odds are slim that those family-oriented men would be interested in having a baby using an embryo that doesn’t include their genetic material!
Briallen’s frozen embryos from donor sperm may enable her to become a mother but, oddly enough, at the expense of becoming a romantic partner.
Egg freezing, by leaving open the possibility of who the father will be, doesn’t have the same impact on the way you feel about love - or on your romantic prospects.
Neither freezing eggs nor freezing embryos is cheap. If your financial resources are limited, your choice between freezing eggs and embryos may depend on what procedures - if any - your insurance covers.
For Briallen Hopper, mentioned above, the financial aspect was critical in her decision. Egg freezing was prohibitive, but IVF was covered by her insurance, putting the embryo freezing process within reach.
Freeze eggs? Freeze embryos? It’s not a simple choice. You need to make a decision that includes your present and your future, your hopes and wishes, and your reality.
We hope that the different factors here leave you more informed about what the pros and cons of each process are. And we wish you clarity and satisfaction with your decision.
You’ve probably heard the phrase “The clock is ticking…” so often that it’s nauseating - or at best ultra-cliché. But for women who have bearing children on their radar, the ‘ticking’ feeling can’t be just brushed off as a nothing. The complexities of fitting in career advancement, the search for an ideal partner and other life complications all before having a child means that that “ticking clock” isn’t just an annoying joke; it’s a legitimate concern. While fertility doesn’t suddenly disappear in a poof of smoke, neither does it last forever - and the process of fertility decline starts in one’s 30s. Here’s why - and here’s what you can (and can’t) do about it.
A woman’s supply of fertile eggs is not constant over her lifetime. While an adolescent girl has approximately 400,000 eggs available, these numbers taper quickly. Dr. Sherman Schreiber, author of “Beating Your Biological Clock,” explains that once a teen starts her menstrual cycle, she loses 1,000 immature eggs every month, and that this loss is simply a biological process, not something that can be changed by factors over which we have control. The average woman has around 25,000 eggs available at age 37 and only 1,000 at age 51. One might still think - hey! In order to conceive a child, only ONE healthy egg is necessary. So those numbers still sound pretty high. But successful conception is not only a numbers game.
Not all eggs are created equal. In order for an egg cell to be ready to be fertilized, it must undergo several cell divisions first. In the complex, amazing process that is cell division, the chromosomes must replicate themselves, then be split perfectly as the cell divides into two. As egg cells get older, they have more difficulty with the division process. One issue can occur with the chromosomes themselves. They separate too early in the process of cell division, giving the resulting egg the wrong number of chromosomes - called aneuploidy. Another issue can occur with the parts of the cell that surround the chromosomes and make them line up correctly during cell division. In aging egg cells, these parts - called the microtubules - often have less control over the process, and end up - again - giving the resulting egg the wrong number of chromosomes.
What happens to an egg cell with the wrong number of chromosomes? It may either:
Bottom line? While plenty of older women do bear healthy children naturally, the older an egg cell gets, its chances of abnormal development increase, and its chances of resulting in a healthy birth decrease.
Professor Greg Fitzharris suggests that in the future, we might be able to take the chromosomes from an older woman’s cell and put them into the cell of a younger woman. That way, the genetic material would remain entirely yours (NOT like getting a “donor egg cell” today), but the younger cell microtubules would make the chromosome division more successful. Exciting as that sounds, it’s still far off. But women who are thinking in advance about fertility can effectively preserve their egg cells’ youth - even today. Women who freeze some of their eggs when they’re in their early 30s, for example, can use them in their 40s when they decide it’s the right time for parenthood. This freezing process is called mature oocyte cryopreservation and it is done in fertility clinics around the world. Freezing eggs effectively stops the clock, retaining the quality in both the chromosomes and the surrounding cell matter. It’s one of the best solutions we have today for preserving fertility. While there are never any guarantees, being aware of the options, anticipating and planning ahead are the best steps you can take to make your motherhood dreams can come true.
