4bb means that the quality of the blastocyst is 4bb, which has nothing to do with whether it is a boy or a girl. The 4 in 4bb stands for stage 4, and the first “b” refers to an endocytosis of “grade B”, which means that the endocytes are few in number and loosely arranged, while the second “b” of 4bb refers to an ectodermal trophoblast of “grade B”, which means that the trophoblast cells are few in number and loosely arranged. The second “b” refers to the ectodermal trophoblast, which is a “grade B”, meaning that the trophoblast cells are fewer in number and more sparsely arranged.4bb blastocysts are used to assess the quality of the blastocyst, indicating that it is a good quality blastocyst, and are not used to determine the sex of the embryo and cannot be determined by this assessment. Embryonic development is a dynamic process. Embryologists have evaluated embryos at the cleavage stage and blastocyst stage based on the morphology of the embryo, respectively. 4bb blastocyst is an evaluation of the blastocyst stage embryo. Pregnant women are advised to adjust their mindset under the guidance of the doctor, no matter it is a boy or a girl, as long as the baby is healthy is the best.