Synchronizing preimplantation embryo development up to the blastocyst stage with uterine differentiation to the receptive state is an absolute requirement for successful implantation. Molecular ...

Around day five or six, the embryo reaches a stage called the blastocyst. At this point, it begins to break out of its outer shell, called the zona pellucida. This process is called hatching ...

the young embryo "hatches" from this protective cover. "During this critical time window, extra sperm can intrude into the ...