човешки клетки под микроскоп


Specialised procedures - eggs

After egg retrieval, embryologists collect the eggs from the follicular fluid, confirm the number of collected eggs and select the ones that are fit for fertilization.


After egg retrieval, embryologists collect the eggs from the follicular fluid which was aspirated from the ovaries. Eggs are counted, washed and transferred to Petri dishes with a special nourishing medium. The Petri dishes are placed in an incubator where egg maturation continues.

Embryollogists confirm the number of collected eggs and select the ones that are fit for fertilization, transfer them into Petri dishes containing a special nourishing medium, and place them inside ihncubators where their maturation continues.

In some patients, very low fertilization rates or no fertilization are observed in a previous ICSI procedure. In these cases, oocytes can be incubated in a special medium containing calcium ionophores. Oocyte calcium deficiency is one of the possible causes of failed oocyte activation after intracytoplasmic sperm injection.

Cryopreservation is used to maintain the viability of cells over long periods. It is achieved by freezing and liquid nitrogen storage at ultralow temperatures – 196°C. At Nadezhda hospital, we employ vitrification, the most modern and effective cryopreservation technique. Vitrification is a freezing method with ultra-fast cooling rates. Upon contact with liquid nitrogen, the intracellular water transitions into a glass-like (vitrified) state without forming ice crystals. Ice crystal formation is the leading cause of loss of cell viability if freezing is attempted with no special cryoprotectants or techniques. In vitrification, commercially developed media are used to replace a part of intracellular water with cryoprotectants. In this way, cells have additional protection from cryogenic damage. After incubation in a cryoprotectant solution, the oocytes or embryos are placed onto special devices (the so-called straws) and directly submerged into liquid nitrogen. The technique is highly reliable, yielding more than 95% preserved viability and development potential, both in embryos and oocytes.
Through the ‘Keep Hope Alive’ project, Nadezhda Hospital is actively engaged in fertility preservation for cancer patients and patients with autoimmune and rheumatoid diseases.


You will sign a contract for egg cryopreservation and storage, which specifies all the conditions of freezing and the period of storage of part or all of the viable genetic material, the rights and obligations of the parties, the methods of payment and termination of the contract. After the expiry of the contract, if you so wish, it may be extended by signing an annex. If you require any assistance or further information, please contact tel. 0887 701 927.




In accordance with Regulation No. H-2 of 12 July 2023 on assisted reproduction activities of the Ministry of Health

Art. 71. Good reasons for the withdrawal and destruction of ova, spermatozoa and zygotes are:


  1. the written certified wish of the patients;
  1. the expiry of the maximum storage period requested by the patients when signing the declaration of informed consent prior to cryopreservation;
  1. the risk of cross-contamination or transmission of bacterial or mycotic infection;
  1. the risk of cross-contamination or transmission of a transmissible disease (HIV, hepatitis B and C, syphilis, etc.);
  1. the expiry of more than 6 months after the requested storage period for unclaimed sperm, ova or zygotes;
  1. the death of the spouse/partner, irrespective of the existence of a declared wish during his/her lifetime, in respect of spermatozoa or zygotes, except in the cases referred to in paragraph 5.9 of Section IV of Annex 1 to Art. 1, т. 1;
  1. the death of the spouse/partner, notwithstanding the existence of a declared wish during lifetime, in respect of oocytes or zygotes;
  1. the establishment of a disease in an anonymous donor which can be transmitted to the offspring or the recipient;
  1. the impossibility of securely identifying donors or tracing the path of genetic material due to incorrect or missing labelling or confusion during processing.

See also

Assisted reproduction technology - fertilization
Specialised procedures - embryo
Specialised procedures - sperm
Fertility preservation