Freeze-all strategy — why do we sometimes delay embryo transfer?
What does “freeze-all” mean?
Freeze-all (or “freezing all embryos”) is a strategy in which no embryo transfer is done in the same cycle in which the embryos were created, and all viable blastocysts are frozen and returned to a later, carefully prepared cycle. This practice is increasingly being applied in modern reproductive medicine — not because we can't make a transfer right away, but because sometimes it's better to wait.
When is the freeze-all strategy applied?
- Hyperstimulation risk (OHSS);
- Increased progesterone before puncture;
- Poorly prepared endometrium;
- Genetic testing of embryos (PGT);
- Personal or logistical reasons.
The theory of cryotreatment of embryos
In recent years, more and more data have been accumulating that pregnancy often occurs more easily in a cryocycle than in a fresh return. This is the basis of the so-called “embryo cryotherapy theory”.
With stimulation with hormones, as in the in vitro cycle, a woman's body goes through unphysiologically high levels of estrogen and progesterone, which sometimes have a negative effect on endometrial receptivity. When we postpone the transfer:
- the body is recovering;
- the hormonal profile is closer to the natural;
- the endometrium can be better synchronized with the moment of transfer.
Our team created this theory in 2017 and we are among the pioneers in applying it in clinical practice.
Freeze-all and the phenomenon of hormesis
Hormesis is a phenomenon in which mild, brief stress leads to a positive adaptation of cells or organism. In reproductive medicine, this means that certain minimal loads—such as stimulation, puncture, laboratory manipulation, or the freezing and thawing process itself—can trigger increased resistance and “selection” of stronger embryos.
In the context of freeze-all:
- The stimulated cycle loads the mucous membrane, but upon recovery it becomes more receptive;
- Freezing/thawing separates the embryos with the greatest vital potential;
- The organism enters a state of adaptation, which sometimes improves the chances of implantation.
Advantages of freeze-all
- Higher chance of implantation in certain patients;
- Safer approach at risk of hyperstimulation syndrome (OHSS);
- Possibility of better personalization of the transfer;
- Allows the use of preimplantation genetic (PGT) or other tests;
- Gives the body time to fully recover.
Are there any disadvantages?
- Requires an additional cycle and sometimes more patience;
- Involves additional costs — freezing, storage, new transfer;
- Not suitable for every patient — individual assessment is required.
What is cryotransfer?
1. Endometrial preparation — through hormone therapy or in a natural cycle;
2. Thawing of the selected embryo;
3. Transfer of the embryo at the right time;
4. Waiting for the result — pregnancy test after 7—10 days.
Conclusion
Freeze-all is not a retreat, but a strategic move based on medical logic and scientific experience. In some cases, this is the best way to give the embryo a chance at the most appropriate time and in the best environment.
Our team created the cryotherapy theory in 2017, which laid the scientific foundation for the freeze-all strategy and its clinical benefits. We believe that an individual approach, careful assessment and the time given to the body for recovery often lead to more successful and peaceful pregnancies.