Fig. 2.

Representative images of calculated blastocyst categories: A1 blastocyst: early blastocyst (blastocoel filling greater than half of the volume of the conceptus), but without overall increase in size more than half as compared to earlier stages. It should possess cells that suggest the formation of an inner cell mass. A2 blastocyst: a true blastocyst with slight expansion in overall size and some thinning of the zona pellucida. A3 blastocyst: full blastocyst with overall fully enlarged and a very thin zona pellucida