Cultivation of embryos
This procedure applies to embryos fertilized after oocytes collection, as well as to embryos cultivation after cryopreservation.
The purpose of embryo cultivation in assisted reproduction is to ensure the closest possible conditions for embryo development similar to those in the mother’s body. Culture media are used, the composition of which ensures all the metabolic demands of the embryo and minimizes the stress for the cultured embryos under the in vitro conditions.
In order to optimize the development of the embryo, fluctuations of the culture conditions are minimized, i.e. pH, osmolality, and temperature.
Morphological evaluation is based on the visual check of the embryo development. It serves the purpose of choosing the best embryo for the transfer. In the morphological evaluation, embryos are qualified by:
• the number of cells
• size, shape, and symmetry of the blastomeres
• scope and locatlization of fragmentation
• quality of the cytoplasm, possible granulation, the presence of the vacuoles
• presence of multinuclear cells
• zona pellucida thickness
The evaluation is subjective and depends on the experience of the embryologist. It starts from the second day after fertilization of the oocytes and lasts until the transfer. During this period, the embryologist assesses the development potential of each embryo, based on the observation of selected parameters. In prolonged cultivation to the expanded blastocyst stage, the embryologist has an embryo longer under their surveillance. Morphology of the 5-day embryo has a greater predictive value on the embryo implantation potential. Selection of the best embryos must be safe, non-invasive, and easy to perform.