Why do some IVF patients need to freeze their embryos instead of having a transfer straight after egg collection? In this insightful webinar, Dr Mariliz Hatzipanteli, Infertility Specialist at Newlife IVF Greece, explains the science behind Freeze-All strategies and why delaying embryo transfer can often improve safety and treatment outcomes.
Hosted by Liadh Fitzgerald, CEO & Founder of Women’s Health Network, this session combines expert guidance with real patient experiences to help you better understand modern IVF treatment planning.
For many patients starting IVF, the biggest surprise is that embryo transfer does not always happen in the same treatment cycle, and as Dr Mariliz Hatzipanteli makes clear, a freeze-all strategy is now a routine part of modern IVF planning.
In IVF, eggs are collected from the ovaries and fertilised with sperm in the laboratory, either through conventional IVF or ICSI. The resulting embryos are watched as they grow until they reach the blastocyst stage, usually after five or six days. If everything lines up on day 5, a fresh transfer may be possible.
But that is only one path. In a freeze-all cycle, no embryo is transferred during the same stimulation cycle. Instead, all embryos are frozen, and one or more are transferred later in a frozen embryo transfer cycle.
That delay is not a setback. In many cases, it is the safer and more practical option. Freeze-all has become very common, especially when doctors want to reduce treatment risks or when the couple has chosen PGT-A. At Newlife IVF Greece, it is one of the most common approaches.
The reason is simple: the IVF cycle that produces embryos is not always the best cycle for pregnancy. Ovarian stimulation can put stress on the body, and sometimes the uterus is better prepared after recovery rather than immediately after egg collection. For patients who expected a transfer right away, that can feel disappointing. Still, the decision is usually made to improve safety or to fit the treatment to the biology of that particular cycle.
One of the most common reasons to freeze all embryos is the risk of ovarian hyperstimulation syndrome. Women with good ovarian reserve can respond very strongly to stimulation and become high responders. Young women with low BMI are at higher risk.
Doctors also look at what is happening in the ovaries and in blood hormone levels on the day of trigger. Too many follicles measuring over 11 millimetres and increased estrogen levels can push a cycle into a higher-risk category. When those signs are present, a fresh transfer should be avoided.
This is where freeze-all changes the tone of treatment. Instead of pushing ahead in a cycle that may be medically unwise, the embryos are preserved, and the body is given time to recover. That recovery period matters not only for safety, but also because it may improve the condition of the uterus before transfer.
Another hormone issue can also change the plan. If progesterone is elevated during stimulation, fresh transfer may no longer be the best option. In that situation, too, freezing embryos and transferring later can make more sense than trying to proceed on schedule.
For patients, the practical message is that a delayed transfer often means the clinic is responding to the cycle carefully, not that something has gone wrong. IVF is highly timed, but it is also highly individualised.
The other major reason embryos are frozen is PGT-A. When couples choose genetic testing, embryos are biopsied, and the results usually take a few weeks. That timing alone makes a fresh transfer impossible.
This is especially relevant for patients who are trying to improve embryo selection, including some women of advanced age who may need several cycles before obtaining a normal embryo. In those cases, freezing is not just a scheduling tool. It is built into the treatment strategy.
One patient, 42 years old, had no significant sperm issues and collected 10 eggs, which resulted in 4 embryos. After PGT, a frozen embryo transfer led to the live birth of a healthy baby girl. When embryos are normal, the success rate is 50% to 60%.
That figure does not erase the uncertainty of IVF, but it helps explain why many couples are willing to wait for testing results rather than transfer immediately. The goal is not speed alone. It is choosing the right embryo at the right time.
Many patients still worry that freezing embryos means losing momentum or lowering their chances. The available evidence in these notes points in the opposite direction. Pregnancy rates with frozen embryo transfer are similar to those with fresh transfer. Recent papers may suggest a benefit to frozen transfer, but current recommendations indicate similar chances of pregnancy with both.
For live birth outcomes, there is not enough evidence to say there is a difference. What is clear is that many children have already been born from frozen embryos.
The technical side of freezing has also changed the conversation. As clinics have increasingly moved to blastocyst transfer on day 5 or day 6, concerns about embryos being lost during freezing and thawing have become much smaller. Blastocyst survival after thawing is very high, at 98% to 99%.
That number matters because it reframes the emotional fear many patients have when they hear the word “frozen.” The embryo is not being put at unusual risk simply because transfer is delayed. In current practice, thaw survival is high, and the risk of losing blastocysts during thawing is low.
There is also a practical advantage to separating embryo creation from embryo transfer. Frozen transfer reduces the risk of complications linked to ovarian stimulation, and many clinics prefer the flexibility of preparing the uterus more carefully in a later cycle.
The hardest part of freeze-all for many patients is not the science. It is the pause.
After egg collection, a withdrawal bleed is expected in about a week, although it is not expected to be a regular bleed. The transfer can then be planned in the subsequent cycle, which is approximately one month or 40 days later. That may not sound long in calendar terms, but for patients eager to become pregnant, even one or two months can feel significant.
This is one reason frozen transfer can be emotionally complicated. Some patients, especially those travelling from abroad, hope to do everything in one trip. They may be disappointed to learn that treatment will require two separate visits. Others request freeze-all for the opposite reason: they do not want to proceed with a fresh transfer because of scheduling, annual leave, or other commitments.
Once embryos are frozen, the next step depends on the transfer protocol. Some patients will have a medicated cycle. Others may be candidates for a natural cycle, although that requires meeting certain criteria. The plan is individualised and should be discussed with the treating doctor.
One reassuring point is that there is no narrow deadline for using frozen embryos. Transfer can happen the next day or ten years later. The embryos remain stored safely, and the chance of pregnancy is still there.
Freeze-all also plays an important role outside standard IVF timing. For patients facing medical treatment, fertility preservation can become urgent.
This is especially true for patients with cancer who need chemotherapy. In that setting, freezing embryos or eggs may protect the chance of future pregnancy before treatment begins. If a patient has a lifelong partner, freezing embryos may be more appropriate than freezing eggs. But there is an important legal and practical complication: in most countries, if the couple separates, the embryos may not be able to be used.
The patient stories here show how quickly fertility planning can become intertwined with cancer care. A 39-year-old woman diagnosed with breast cancer attended with her partner, but her partner was found to be azoospermic. Six embryos were created, and she later said she would be ready for transfer next year.
Another case involved a 30-year-old woman with very good ovarian reserve whose partner had testicular cancer. The couple underwent ICSI, and sperm straws were preserved for possible future treatment. They now have two embryos remaining after achieving a live birth following the man’s surgery.
These are very different situations, but they show the same principle: freezing can create time when time is otherwise disappearing.
Not every freeze-all cycle is driven by hormone levels or genetic testing. Egg donation is another common reason.
In donation cases, one practical approach is for the male partner to travel first and provide a sperm sample before the eggs are arranged for fertilization. Then, depending on the couple’s wishes, frozen embryo transfer can be scheduled a few months later. Frozen eggs are also being used more and more, although the preferred scenario is often to create embryos, freeze them, and then perform frozen embryo transfer later.
This flexibility is one reason frozen cycles have become so embedded in fertility care. They allow treatment to be adapted not only to medical needs, but also to logistics, travel, and life circumstances. That does not mean every patient prefers them. Many still want a fresh transfer if it is safe and possible. But it does mean frozen transfer is no longer a backup plan reserved for unusual cases.
The rise of freeze-all does not mean fresh transfer has become obsolete. Fresh transfer is still an option when the criteria are right: the woman is well, the uterine lining is good, progesterone is low, estrogen is not too high, and there are suitable day 5 embryos. If a couple has only day 6 embryos, they cannot be used in the first transfer.
That balance matters. Frozen transfer may be common, but it is not automatically better for every patient in every cycle. There is room for both fresh and frozen transfer as long as the clinic is satisfied with the results and the evidence shows they are pretty much equal.
In practice, though, many patients will end up in a frozen pathway because of PGT, because doctors want to eliminate the risk of ovarian stimulation complications, or because the timing of treatment simply works better that way. Freeze-all is not a futuristic add-on to IVF. It is already part of everyday care.
A freeze-all cycle can feel like an unexpected detour when you begin IVF expecting an immediate transfer. In reality, it is often a sign that treatment is being tailored to your body, your safety, and the timing most likely to support pregnancy. Whether the reason is hyperstimulation risk, PGT-A, fertility preservation, or donation, freezing embryos gives doctors and patients more control over when transfer happens.
That extra time can be frustrating. It can also be valuable. In IVF, the fastest route is not always the best one, and for many patients, waiting for a frozen embryo transfer is what makes the cycle safer, more flexible, and ultimately more successful.
It is very common. Freeze-all is one of the most common approaches, especially when there is a risk of hyperstimulation or when PGT-A is involved. It is the most common way at New Life IVF.
If the question is about pregnancy rates, the chances with fresh and frozen transfer are similar. Recent papers suggest there may be a benefit to frozen embryo transfer, but current recommendations indicate similar chances of pregnancy with both.
For live birth outcomes, there is not enough evidence to say there is a difference. Many children have already been born from frozen embryos.
There is room for both fresh and frozen transfer as long as clinics are satisfied with the results and the evidence shows they are pretty much equal. Many women will have PGT, or doctors may want to eliminate the risk of ovarian stimulation because it can be severe.
Freeze-all is not the future, but the present.
Yes and no. Many patients who come from abroad prefer to do everything in one go, so they may be disappointed when they are told they need two different trips. Most people do not necessarily prefer frozen transfer over fresh transfer, because many are eager to become pregnant and even one or two months may feel too long.
Fresh transfer is absolutely possible when the criteria are met. The woman needs to be well, there needs to be a good lining, progesterone must be low, and estrogen should not be too high. Five-day embryos are needed because if a couple has only day 6 embryos, they cannot be used in the first transfer.
Frozen transfer can give more chances because there can be multiple frozen transfer attempts.
The ideal scenario is to let the body recover completely. After egg collection, a withdrawal bleed is expected in about a week. This is not expected to be a regular bleed.
The transfer can be planned in the subsequent cycle, which is approximately 1 month or 40 days.
No. It does not matter whether the transfer is done the next day or 10 years later. The embryos are stored safely and remain frozen in time, so the chances of pregnancy are there.
The next treatment depends on the protocol, and this should be discussed because it can be very personalised. There are medicated and natural cycles, and the natural cycle requires meeting a few criteria.
Several protocols can be considered, but the best option needs to be decided on or at least discussed individually.
If vaccination has been done with the GP at the correct time, it is fine. Some people will never have antibodies. If vaccination was done with the GP at the correct time, ideally at least one month before treatment, it should be fine.
