Freezing eggs and embryos — when, why and how is it done?

Modern reproductive medicine makes it possible not only to treat infertility, but also to plan parenting at a time that is most convenient for a woman or a couple. Freezing eggs and embryos is an extremely valuable tool for preserving reproductive potential.

What is the difference between freezing eggs and embryos?

- Ovules are frozen when the woman does not have a partner or does not wish to fertilize the cells at the moment.
- Embryos are frozen when fertilization with sperm has already been done - during an in vitro procedure.

Egg Freezing — “Fertility Preservation”

When is it appropriate?

- In women between 30—38 years old who postpone motherhood;
- Before chemo- or radiotherapy (oncofertility);
- In case of family burdens with premature menopause;
- In planned operations that affect the ovaries;
- When a woman is not sure if she will have a child, but wants to keep her chances.

What does the procedure involve?

1. Stimulation of the ovaries with hormones (7—10 days);
2. Puncture and extraction of eggs under anesthesia;
3. Assessment of mature eggs;
4. Vitrification — a method of rapid freezing, which guarantees high survival after thawing;
5. Storage in liquid nitrogen at -196°C.

Embryo freezing — during an in vitro procedure

When are embryos frozen?

- When there are more than embryos of good quality after transfer;
- In case of postponement of the transfer for medical or logistical reasons;
- With a high risk of hyperstimulation — transfer is postponed for the next cycle;
- When genetic testing (PGT) is done and waiting for the result;
- In donor cycles.

How is it going?

1. Embryos are cultured until day 5/6 (blastocyst);
2. Quality assessment is carried out;
3. Selected embryos are vitrified;
4. They are stored for transfer at the next appropriate time.

How long can eggs and embryos be stored?

In practice — indefinitely, as long as the conditions in the laboratory are optimal. Data show successful pregnancies after 10+ years of storage. According to Bulgarian legislation, the recommended storage is 5 years.

What is the success rate after defrosting?

- Modern methods of vitrification allow more than 90— 95% survival;
- Frozen embryos often give a success rate comparable to freshly cultured ones;
- Frozen eggs lead to a lower chance compared to embryos, but in women under 35 the results are excellent.

Eggs or Embryos — Which is Better?

Depends on the situation:
- Without a partner or unclear future — eggs;
- With a partner or with donor sperm - embryos;
- Legally and ethically — the egg is personal, but the embryo is “of the couple” — in sections this can be a delicate topic.

Conclusion

Freezing eggs and embryos gives a chance to control the time and circumstances in which you will create a child. In our clinic we have a high-tech cryo-laboratory and an individual approach to each patient, because each reproductive history is unique.

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