The quality of day 5 blastocysts 3bb and 4bb is basically the same, but 4bb blastocysts have been cultivated in vitro for a longer period of time and are relatively more suitable for transplantation.
The classification of blastocysts consists of six numerical grades from 1 to 6, which represent the duration of blastocyst in vitro incubation; a, b and c are determined by the quality grade of the internal cell mass of the blastocyst and the quality grade of the trophoblast cells.
For 3bb blastocysts and 4bb blastocysts, because their cell mass and trophectoderm both belong to grade b, their quality are both medium quality blastocysts, which belong to the range of transferable, and the quality of blastocysts is basically the same.
4bb blastocysts are longer than 3bb blastocysts cultivated in vitro, the blastocyst cavity is full of blastocysts, and the success rate of transplantation is relatively higher than that of 3bb blastocysts. The specific transplantation situation still needs to be judged by the clinician according to the patient’s individual situation.