In vitro fertilization and embryo transfer (IVFET) technology, commonly known as in vitro fertilization, refers to the removal of eggs and sperm from the living body through in vitro fertilization, culture, split into two to eight dividing spheres or blastocyst stage, and then transferred to the female uterus to bed, develop into a fetus and give birth. It is a high, precise and advanced technology. It is not only a milestone in the history of infertility treatment, but also has broad prospects for basic research in reproductive medicine, early embryology, genetics and molecular biology, and is of great significance for family planning and eugenics. What is embryo culture? If the conditions are right, fertilization of the sperm and egg is completed in the incubator in about 18 hours. After a few hours, the fertilized egg divides into two cells, and after 48 hours, each embryonic precursor usually has two to four cells, at which point the embryo can leave the incubator and be placed in the female uterus. The process that the fertilized egg undergoes in the incubator is called embryo culture. After fertilization, the egg will continue to be cultured in vitro. During this process, the fertilized egg begins to divide, from one cell (the fertilized egg), into two cells, and then continues to divide into four and eight cells …… The embryo is usually transferred to the mother’s uterus after 24-48 hours of culture (i.e. 48-72 hours after egg retrieval), when the embryo is in the 4-8 cell stage. The duration of embryo culture may vary, and in some patients embryos are even cultured in vitro until the 5th day before implantation into the body. This extended culture is called blastocyst culture. Embryo quality – separately The quality of development may be different for each embryo for reasons that are difficult to control. During the culture process, we will observe the embryos under a microscope to judge the quality of the culture results. Of course, this judgment is not absolute, just as in the case of a person who appears healthy on the surface, its internal problems may not always be visible. The quality of the embryos is usually rated by looking at their character under the microscope. For example, a 4-cell stage embryo can be classified into 4 grades: Grade 1: 4 complete and uniform oogonia (embryonic cells) can be seen in the embryo; Grade 2: 3 complete and uniform oogonia can be seen in the embryo, while the other cell may have broken into pieces; Grade 3: 2 complete and uniform oogonia can be seen in the embryo; Grade 4: only 1 complete and uniform oogonia can be seen in the embryo. The better 1-3 embryos from the cultured embryos will usually be selected for transfer to the mother’s uterus. If there are any extra good embryos, they can be frozen and stored as needed and transferred again at a later time when appropriate. Embryo transfer is usually performed on an outpatient basis without anesthesia and may be mildly sedated for nervous patients. The patient is usually placed in the gynecologic examination position with a lithotomy. The doctor exposes the cervix with a speculum, aspirates a culture containing one or more fertilized eggs through a thin sterile transfer tube with a syringe attached, and then gently places the transfer tube into the uterine cavity where the culture containing the fertilized eggs is placed. One or more embryos can be transferred at a time. Usually, the untransferred embryos can be refrigerated for the next meltdown and then transferred, although the doctor should explain to the patient that the entire transfer takes 10 to 20 minutes and that the patient should preferably stay in bed for about an hour after the transfer.