The culture of fertilized oocytes is performed in special nutritional material and the resulting embryos are kept in special incubators, where they are preserved under fine conditions, until the day of transfer in the woman’s uterus.

The number of zygotes (fertilized oocytes) is checked 16-20 hours after fertilization. Fertilized oocytes are those which contain 2 PN bodies (one with the mother’s DNA and the other with the father’s DNA). Subsequently, zygotes are cultured in the lab until the day of embryo transfer which is determined on the basis of the number and morphology of available embryos.

Embryo Transfer is done on the 2nd or 3rd day after oocyte collection. When possible, culture of embryos is done until the 5th day. This stage of embryonic development is called blastocyst.