ABSTRACT
Obligatory requirements for the successful completion of normal fertilization include a mature, metaphase II oocyte and motile spermatozoa that have completed the process of capacitation. The newly formed zygote undergoes early cleavage divisions depending upon the oocyte’s endogenous machinery, and at the 4-8-cell stage initiates transcription of the embryonic genome1. In vivo, these processes are synchronized with the preparation of the endometrial mucosa (window of implantation), thereby ensuring an adequate milieu receptive to the blastocyst.
