IVF employing no drugs for ovarian hyperstimulation, whilst medications for ovulation suppression may still be used. Throughout early blastocyst growth, fluid starts to fill embryo. The embryo begins to develop like a balloon. To implant, the embryo should escape from the shell surrounding it. This is referred to as "hatching." https://linkingbookmark.com/story18335289/what-does-in-vitro-fertilization-mean