Great Egg-spectations: Understanding your individual chances of having a child using frozen eggs

Alex Armstrong

Egg freezing has become increasingly popular since it dropped its “experimental” label just over a decade ago. Despite the growth in popularity, the process can be trying. There’s the financial expense, the emotional investment, and the physically taxing procedure.

For many, the costs are justifiable for what they view as an insurance policy. They may not be in a place to have children now, or even make a decision about it, but freezing their eggs can keep that option available for years to come.

However, many steps need to go right between freezing your eggs and having a baby. That’s why it’s important to understand the factors that play a role in each step along the way, and what their chances of success are.

In this post, we’ll answer the following questions:

WILL I HAVE A CHILD IF I FREEZE MY EGGS?

Egg freezing works. The American Reproductive Society removed its experimental label after data from 100+ studies indicated that the technique’s pregnancy rates are equivalent to those of fresh eggs. Equally as important, egg freezing doesn’t increase the rates of chromosomal abnormalities or birth defects in the children born using the technique.

Remember that egg freezing only provides a future chance of having a baby – it’s not a sure thing. Though reproductive technologies are continuing to advance, it’s important to consider that even in natural conception not every fertilized egg results in a child.

Even if you retrieve a large number of eggs (a typical practice in egg freezing), that doesn’t guarantee a successful pregnancy amongst the group of them. There are many other factors to consider, including the quality of your eggs and that of the contributing sperm

HOW LIKELY AM I TO HAVE A CHILD?

Most fertility providers use egg outcome calculators — the same ones you’re able to access online — to estimate your probability of having a child. These calculations are based on your input of two data points — your age and the number of eggs you’re able to retrieve for freezing — along with other statistical factors.

While these provide a great baseline for understanding your odds, they don’t tell the whole story. Genetics and lifestyle have a weighty role to play as well.

Smoking is just one of these factors. Exposure to cigarette smoke can increase egg loss, making current and former smokers more likely to experience early menopause before age 45.

The good news is that the effects of smoking are dose-dependent. For example, if you were a “social smoker,” your fertility is less likely to be affected than someone who’s smoked a pack a day for the last two decades.

Beyond smoking, poor sleep, having a higher BMI, exercising excessively, and alcohol use have all been proven to correlate with your reproductive health. Traditionally, these factors aren’t included in fertility calculations because they’re difficult to quantify. However, they’re still important considerations to help understand your ultimate chances of success.

WHAT’S INVOLVED IN THESE ONLINE EGG OUTCOME CALCULATIONS?

Live birth calculations are based on the results of scientific studies that aggregate data from past fertility patients. The data points include the number of eggs retrieved, the age of patients at the time of egg retrieval, and whether a live birth resulted from those eggs.

The calculators’ formulas can then use that information to determine a live birth prediction for any combination of age and egg quantity that’s entered.

One key study commonly used in the calculations tracked the development of 1,283 eggs from the process of freezing and thawing, all the way to live birth. Based on the data, the estimated live birth rate for this cohort was about 6.4% for each frozen egg.

Researchers were able to get more granular results based on the patient’s age at the time of egg retrieval. What they found was that women under 30 saw a live birth rate of 7.4% per thawed egg, while those between the ages of 30 and 34 had chances closer to 7.0% for each.

For women between 35 and 37, that number dropped to 6.5%, while those over 38 saw a further reduction in their chances of having a live birth — a 5.2% chance per thawed egg.

In other words, the study concluded that the average chances of live birth for one frozen egg declined as the patient’s age increased, after the age of 30.

But, while these types of egg calculators are often used by fertility doctors as a key element of the standard of care, aggregate data can’t determine an individual’s unique status. Individuals in a category aren’t all the same. Not only that, but it also takes time to build up a nuanced picture with data. This can be hard to do at this stage as egg freezing is still a relatively new procedure.

Moreover, there’s a lag between when people freeze their eggs and when they use them. This limits the amount of information available today about frozen eggs that actually resulted in a baby. As of now, this generalized data only sketches the broad outlines of predicting your chances.

In contrast, our research at Future Fertility shows that individual predictions are more varied. We see that the quality of individual eggs isn’t all good or all bad for a certain age group. Egg quality also varies within the same person, with differences shown across cycles or even varying between eggs within the same retrieval cycle. As in other areas of medicine, your personal health, genetics and lifestyle habits matter too, in addition to your age.

HOW MANY EGGS SHOULD I AIM TO FREEZE?

To help answer this question, consider what probability would make you feel comfortable about your decision to invest in egg freezing. Would you feel good about a 50% chance of having a baby – for your time, effort, and money? Would you be willing to invest more over multiple cycles to reach 70%?

You’re born with all the eggs you’ll ever have. Each month that passes, the number of eggs in your ovaries diminishes, and in your 30s, your egg quality starts to decline as well. This gives you less opportunity later in life to retrieve the high-quality eggs most likely to produce genetically normal embryos.

Using an online egg calculator to provide an example, at age 33, freezing 10 eggs provides a 69% chance of having a child. Fast forward five years and the picture looks different: 20 eggs is the magic number recommended at 38 to give you the same probability of success. If you were to freeze 20 eggs at the younger age of 33, your chances would improve from 69% (for 10 eggs) to 90%.

HOW DO I INTERPRET THE PROBABILITY OF LIVE BIRTH?

It’s understandable to want to know your chances of having a child before undertaking an intensive process like freezing your eggs. However, even if you retrieve the target number of eggs, freezing them doesn’t guarantee a pregnancy, let alone a live birth.

Once frozen, each egg has to make it through the process of thawing, fertilization, embryonic development, implantation, pregnancy, and finally, live birth. This process isn’t seamless and any of these steps may fail, preventing ultimate success.

For starters, not all eggs survive thawing. One study found that 1.7% of patients ended up in the unfortunate position of having none of their eggs survive the thawing process. And, once thawed, not all are high-quality enough to use.

Although the majority of eggs thaw without issue, their number is further winnowed down at the next stage as not all are successfully fertilized. Moreover, some of the ones that do progress to blastocyst-stage embryos may be chromosomally abnormal.

Even if you have several healthy embryos, or blastocysts, there are a limited number that can be implanted. Usually only one or two — a maximum of three for women over 40 — go on to this stage.

And implantation isn’t the end of the road — there’s the entire pregnancy to get through too.

It’s macabre to think about, but somewhere between 15 to 25% of pregnancies end in miscarriage.

Each step of this big undertaking comes with its own risks and level of attrition. However, since patient populations vary, different clinics and even different physicians have their own respective success rates, attributable to different factors.

For example, one clinic may have a larger cohort of younger patients. Another might see a greater number of clients undergoing oncology-related fertility preservation. In addition, since egg freezing is done by hand, results can vary even when everyone is following the same protocols.

Given these differences, it’s best to speak with the team at your fertility centre to better understand their success rates.

HOW MANY MATURE EGGS CAN I EXPECT TO FREEZE PER CYCLE?

The number of mature eggs you can expect to freeze each cycle depends partly on your age.

Individuals under 35 without fertility issues can expect to retrieve an average of 15 eggs per cycle. But, as we saw with live birth predictions lowering with age, population data also shows that the number of eggs retrieved per cycle decreases as well. Therefore, an older patient may require multiple freezing cycles to achieve the same chance of success that a younger patient could achieve in a single cycle.

Using the same calculator as our previous example, if you undergo a single cycle at the age of 33 and are able to retrieve 15 eggs, you have a good chance of having a child at 83%.

To reach that same 83% chance of having a live birth, it’s recommended that a 38-year-old freeze 30 eggs — a number that may take three cycles to retrieve.

(Keep in mind that these predictions are based on generalized data instead of individual egg quality and don’t account for your personal health factors.)

Given the physical and emotional costs — not to mention the financial expense — of a single cycle, undergoing additional cycles is likely worthwhile, particularly if you’re in an older age group. While it’s a personal decision, many find the increased chance of having a child is worth the trade-off of going through multiple cycles.

HOW CAN I ASSESS THE QUALITY OF MY EGGS?

Online egg calculators can be misleading because they’re only predicting the likelihood of having a baby using your age and the number of eggs you retrieve. But even if you’re able to retrieve that ideal number of eggs, your chance of success may differ depending on their quality compared to other people in your age category.

While semen quality analysis is a standard part of fertility medicine, traditionally, there’s been no objective or agreed-upon way to assess egg quality in the fertility lab. As a group, embryologists haven’t been able to consistently differentiate between a good egg and a bad egg when looking at them under the microscope.

Our VIOLET™ technology is filling this gap in care. VIOLET™ is the first tool of its kind that uses artificial intelligence (AI) to predict the likelihood of each of your eggs forming a healthy usable embryo (a blastocyst).

VIOLET™’s algorithm leverages over 120,000 egg images and their outcome data (i.e., Did the egg in the image fertilize and form a blastocyst?) across different patient types and geographies. The type of AI VIOLET™ uses, called Deep Learning, enables it to recognize patterns that are otherwise invisible to the human eye.

VIOLET™ reports can be provided to you by your clinic to empower you with more personalized insights into the quality of your frozen eggs. Each report provides images of your eggs along with personalized predictions of blastocyst formation for each egg.

The report also uses your personal egg quality assessment to tailor live birth predictions to your data – helping you to better understand your own likelihood of success versus the generalized predictions you receive using online egg calculators. Even better, it doesn’t require you to undergo any additional procedures and poses no additional risk to your eggs.

Armed with information about your individual egg quality, you and your doctor can determine if more egg freezing cycles are needed in an effort to get you closer to an expectation of live birth that you’re comfortable with.

Photo credit: Ekaterina Bolovtsova