One of the most common questions I hear from patients is: “Should I freeze embryos now if I want another child later?” It’s a smart and important question. Life doesn’t always line up neatly with biology, and many of us are building careers, managing relationships, or facing medical issues that make timing a challenge.
Both freezing eggs and freezing embryos can preserve fertility, but they aren’t the same. Each comes with its own advantages and challenges, and the best choice depends on your stage of life, your relationships, and your long-term goals.
In this post, I want to focus on embryo freezing—how it works, why timing matters, and what I’ve seen matter most for women considering this step.
Freezing Eggs vs. Freezing Embryos: Why the Difference Matters for Your Fertility
A common misconception is that women lose just one egg per month. In reality, the ovaries lose about 30 eggs every day—around 900 each month—most of which dissolve naturally, with only one typically maturing for ovulation (Journal of Ovarian Research, 2017). That steady loss means a woman is constantly using up her egg supply, even when she’s not trying to get pregnant.
Here’s how egg numbers decline over time:
- 20 weeks of gestation: 6–7 million eggs
- At birth: 1–2 million
- Puberty: 300,000–500,000
- Age 32: ~120,000
- Age 37: ~25,000
- Menopause: <1,000 (ACOG, 2014)
For women, what this means is that even though you may still have eggs left in your 30s and 40s, the number and quality of those eggs shrink dramatically. By your mid-30s, the odds of retrieving enough healthy eggs in a fertility cycle start to drop, and by 40, the average retrieval may yield only 8 eggs—compared to 25 eggs at age 30 (Medical News Today, 2023).
This decline directly impacts fertility treatment outcomes. For example, at age 30, you might need six eggs to create one embryo with a 40% chance of live birth, but only four eggs if you freeze embryos directly (ASRM, 2021). By contrast, at age 40, not only are fewer eggs available, but a much larger percentage will be chromosomally abnormal, making it harder to create embryos that lead to healthy pregnancies.
The takeaway for women: egg loss is constant and irreversible, and while fertility treatments can help, they can’t replace time. That’s why freezing eggs or embryos earlier captures a healthier, more plentiful supply, preserving better options for the future.
Why Freeze Embryos for a Future Child?
Fertility doesn’t wait, and delaying parenthood is increasingly common. In your early 30s, about 10–25% of eggs have chromosomal abnormalities, but by your 40s, this rises to 50–75%, increasing miscarriage risk (NEJM, 2017).
Egg quantity also drops: an IVF cycle at 30 might yield 20–25 eggs, but by 40 you’re often down to 8–10 (Fertility and Sterility, 2018). That’s nearly a ninefold decline over a decade.
Freezing embryos now—ideally before 35—preserves your healthiest options for the future, whether you’re planning multiple children or facing medical treatments like chemotherapy.
Is It Better to Freeze Eggs or Embryos?
One of the most common questions I hear is whether it’s better to freeze eggs or embryos. The truth is, both approaches can preserve fertility, but they serve slightly different purposes depending on your stage of life, relationship status, and future plans. Eggs offer flexibility and independence, while embryos provide more stability and stronger success rates. Understanding the advantages and disadvantages of each can help you decide which is the right fit for your circumstances.
It’s also worth noting that egg freezing is generally simpler. The process involves stimulating your ovaries, retrieving the eggs, and freezing them directly. Once frozen, the eggs simply “wait” until you’re ready to use them.
Embryo freezing, on the other hand, is a greater effort. After retrieval, eggs must be fertilized with sperm, cultured in the lab for 5–7 days, and often genetically tested before freezing. While this adds more steps and decisions, the payoff is greater certainty and stronger odds of success, since you already know which eggs became viable embryos.
Both egg and embryo freezing work, but your situation determines the best choice.
Advantages of Freezing Eggs
- Egg freezing offers flexibility if you don’t yet have a partner or sperm donor.
- It allows you to preserve fertility without committing to fertilization right away.
- For some women, discarding unused eggs feels less ethically complex than discarding embryos.
Disadvantages of Freezing Eggs
- Eggs are more fragile than embryos, since they are single cells, and some may not survive the thawing process.
- Achieving a pregnancy often requires more eggs — research suggests that about 15 or more frozen eggs may be needed to create one healthy embryo (Fertility and Sterility, 2015).
Advantages of Freezing Embryos
- Embryos are more stable, with about 95% surviving thawing compared to ~90% for eggs (ASRM, 2020).
- They typically require fewer eggs — around four at age 30 to reach a 40% live birth chance, compared to six with eggs.
- They offer higher success rates per transfer, with 40–50% live birth rates before age 35, compared to 20–30% at ages 38–40 (Fertility and Sterility, 2018).
- Embryos can be tested with Preimplantation Genetic Testing (PGT) to check chromosomal health before freezing, giving added reassurance.
Disadvantages of Freezing Embryos
- Freezing embryos requires sperm, which can reduce autonomy for single women.
- If embryos are created with a partner, separation later can lead to complex legal and emotional disputes over their use (AJOG, 2016).
- For some people, discarding unused embryos raises ethical or religious concerns, which may influence the decision.
Who Should Consider Embryo Freezing?
Embryo freezing isn’t something every patient needs, but it can be a powerful tool for those who want to preserve their ability to grow their family in the future. It’s especially relevant if you know you may be delaying pregnancy or if you face medical conditions that can make conception more difficult later on. By freezing embryos earlier, you lock in the egg quality and fertility potential of today, rather than facing the reduced odds of tomorrow.
Embryo freezing may be the right choice if you:
- You want more than one child, since freezing embryos gives you a better chance of having enough healthy embryos for multiple pregnancies later.
- You plan to delay pregnancy past age 35, when fertility declines more sharply. For example, monthly conception odds fall from about 20% at age 35 to under 10% by age 40 (ACOG, 2023).
- You have a medical condition that may impact fertility, such as cancer, endometriosis, or autoimmune disease. Freezing embryos provides protection against those risks before treatments or disease progression take a toll.
- You want to preserve your options without feeling pressured, since embryo freezing can give you peace of mind and reduce the stress of “running out of time.”
What’s the Best Age to Freeze Embryos?
When it comes to fertility preservation, timing makes a big difference. While many women conceive naturally in their mid-to-late 30s, the odds of success decline each year because both the quantity and quality of eggs decrease over time. That decline affects not only natural conception but also the results of IVF and embryo freezing. By choosing to freeze embryos earlier, you’re essentially “locking in” the healthier eggs you have now for use later.
The earlier, the better—ideally in your early 30s. Egg quality and quantity peak before 35, giving embryos frozen at this age a 40–50% live birth rate per transfer, compared to 20–30% at 38–40 and under 20% after 40 (Fertility and Sterility, 2018).
Another advantage of freezing embryos over eggs is the option for Preimplantation Genetic Testing (PGT). This testing allows specialists to evaluate whether embryos have the correct number of chromosomes, reducing miscarriage risk and improving pregnancy outcomes. Even though PGT doesn’t guarantee success, it provides additional reassurance that you’re giving yourself the best chance when you decide the time is right (NEJM, 2017).
How Does the Embryo Freezing Process Work?
For many patients, the idea of embryo freezing feels overwhelming at first. In reality, the process is very similar to in vitro fertilization (IVF), and it’s something fertility clinics do routinely. The goal is to carefully stimulate your ovaries, retrieve healthy eggs, and then either fertilize and grow embryos in the lab or freeze the eggs directly. Knowing what to expect step by step can make the process feel much more manageable.
The process typically includes:
- Fertility evaluation – initial testing of ovarian reserve and overall health to make sure you’re a good candidate.
- Cycle synchronization – medications align your ovaries so eggs develop at the same pace.
- Stimulation – daily hormone injections for 10–14 days to grow multiple eggs at once.
- Egg retrieval – a short outpatient procedure under light sedation to collect the eggs.
- Fertilization – eggs are fertilized with sperm (either through standard IVF or ICSI).
- Embryo culture – fertilized eggs grow in the lab for 5–7 days, with monitoring for quality.
- Freezing (vitrification) – embryos are flash-frozen, and about 95% survive thawing with modern techniques (ASRM, 2020).
What Are the Risks of Embryo Freezing?
No medical procedure is without risk, and embryo freezing is no exception. Most of the potential concerns are not from the freezing itself but from the IVF process or underlying fertility issues.
- Studies have shown a slight increase in birth defects (e.g., ~2% baseline vs. ~4% with IVF), but most of this risk relates to patient age and health factors, not the procedure itself (ACOG, 2014).
- Transferring multiple embryos raises the chance of twins or higher-order pregnancies, which can lead to prematurity and complications. This is why single embryo transfer is often recommended (AJOG, 2016).
How Long Can Embryos Stay Frozen?
One of the most reassuring aspects of embryo freezing is that there is no precise “expiration date.” Once embryos are vitrified—frozen with ultra-rapid cooling—they remain in a suspended state where cellular activity is essentially paused. That means time does not appear to weaken them in the way it does unfrozen eggs inside the body.
Healthy pregnancies have been reported after embryos were stored for 10–20 years, and there are even rare cases of success after 25 years in storage (Journal of Assisted Reproduction and Genetics, 2017). Importantly, studies have found no significant differences in survival, implantation, or live birth rates between embryos frozen for a few months versus those frozen for many years.
For patients, this means you can feel confident that embryos created and stored today can remain viable well into the future—whether you use them in two years or twenty.
Lab-Created Embryos vs. Natural Conception
Many people wonder if embryos created in a lab are somehow “different” from those conceived naturally. In truth, the key difference is simply where fertilization and early growth happen. In natural conception, sperm and egg must meet in the fallopian tube, then the embryo must travel to the uterus, implant, and continue to develop. At each of those steps, there are chances for the process to fail.
With IVF, fertilization and growth happen in a controlled lab environment. Embryologists can ensure eggs are fertilized, watch embryos closely as they develop, and transfer only the healthiest ones to the uterus. This avoids many of the hurdles embryos face inside the body.
Research shows that, per egg, IVF is 3–4 times more likely to result in a live birth than natural conception attempts (NEJM, 2017). That’s because embryos in the lab bypass natural barriers like blocked fallopian tubes, poor sperm transport, or timing mismatches with ovulation.
In other words, lab-created embryos are no less “natural” in their biology—they just have the advantage of science helping them past the obstacles that can prevent conception in the body.
PGT Genetic Testing: How It’s Used for Embryo Selection
One of the advantages of embryo freezing over egg freezing is that embryos can be genetically tested before they’re stored. This step, called Preimplantation Genetic Testing (PGT), is sometimes recommended when patients want to reduce the risk of miscarriage, improve the chances of a healthy pregnancy, or avoid passing on inherited genetic conditions. Not everyone needs PGT, but for many families it provides valuable information and reassurance.
Preimplantation Genetic Testing (PGT) helps identify embryos most likely to lead to a successful pregnancy:
- PGT-A: screens for chromosomal abnormalities (e.g., Down syndrome, trisomy 16).
- PGT-M: detects single-gene conditions (e.g., cystic fibrosis, sickle cell).
- PGT-SR: identifies chromosomal rearrangements that can cause miscarriage.
While PGT doesn’t guarantee success, it can reduce miscarriage risk and improve implantation rates, making it a meaningful option for many patients considering embryo freezing (International Journal of Women’s Health, 2020).
Who Else Benefits from Embryo Freezing?
While age is the most common reason patients consider embryo freezing, it’s far from the only one. Embryo preservation can also provide clarity, security, and family-building options in more complex situations.
You may benefit from embryo freezing if you:
- You have a family history of genetic disorders such as Huntington’s disease, fragile X, or cystic fibrosis. With embryo freezing, preimplantation genetic testing (PGT) can be used to avoid passing on those conditions.
- You are about to begin medical treatments that could damage fertility, such as chemotherapy or radiation. Freezing embryos beforehand can safeguard your ability to have children later.
- You are planning to have multiple children and want more consistent outcomes across pregnancies. Having embryos frozen at the same age ensures that future attempts don’t depend on declining egg quality over time.
Embryo Freezing: Key Takeaways for Your Fertility Journey
Embryo freezing is not a one-size-fits-all decision. For some, it’s a proactive step that provides peace of mind and long-term security. For others, it may not be necessary depending on age, health, and family-building goals. What’s most important is that you understand how age and medical factors influence fertility so that you can make a choice that aligns with your values and your future.
Taking action earlier—ideally before 35—gives you the most options for having a second child or beyond. But no matter where you are in your journey, the decision is deeply personal. The best next step is sitting down with a fertility specialist who can evaluate your situation and help guide you through the options.
If you’re planning for a second child, wanting to leave the door open, or even haven’t had your first yet, freezing embryos can be a proactive way to regain direction and control over your fertility. Don’t suffer alone — we are here to answer your questions and help you find peace in the process.
