Patients often ask, “What is IVF blastocyst culture? The IVF technique involves fertilizing the egg and sperm in vitro to form an embryo and then returning it to the uterine cavity. Blastocyst culture is the process of extending the in vitro culture time to select embryos of good quality that can grow into blastocysts. This increases the rate of IVF fertilization and pregnancy rates, and blastocyst culture is a major development in assisted reproductive technology. What is IVF blastocyst culture? Experts explain that blastocyst culture extends the culture time and eliminates inferior embryos. The process of extending embryo culture time naturally eliminates inferior, even defective, embryos so that relatively high-quality embryos stand out and grow into blastocysts. These blastocysts with high clotting power enable a satisfactory pregnancy rate to be achieved with only a small number of embryos implanted, and our center currently has a 65% success rate for selective single blastocyst transfer. After fertilization of the egg, the cells in the embryo will divide and proliferate rapidly in the following days, reaching 8-10 cells on the third day after fertilization, and by the fourth day, not only will the cells divide rapidly, but the embryo will also undergo important metabolic transformations, and by the fifth day, it will reach the blastocyst stage, where the embryo will contain 75-100 cells with increasing capacity. At this point, the blastocyst includes the trophoblast, the blastocyst cavity and the inner cell mass. The trophoblastic ectoderm will form the placenta, membranes and umbilical cord, while the inner cell mass will form the fetus. We cannot judge an embryo by its appearance alone; embryos in in vitro culture are in the process of transformation and repair and therefore may produce fragments, which are small fragments that have been pruned away during cell division, as well as vacuoles, which are small gaps located within the cell parenchyma that may not appear to be good quality embryos, but may still go on to develop into an ideal healthy pregnancy. Although many embryos develop to day 2 or 3, forming a 4- to 8-cell stage, only the strongest embryos will develop to day 5 to form a blastocyst and eventually a fetus. Identifying good embryos is not an easy task and can only be better identified when the embryo has reached a certain stage of development, such as the blastocyst stage. The success rate of developing a blastocyst into a fetus in culture for 5 days will be significantly higher, nearly twice that of a 3-day embryo in culture. What kind of embryos can develop into blastocysts? The factors that influence embryo development are energy and chromosomes. First, energy. The embryo’s source of energy is primarily the fine structures inside its cells, the mitochondria. The embryo depends on the mitochondria it inherits from the egg for energy to survive until it implants and forms the placenta. All mitochondria of the embryo are derived from the egg. However, since the primordial follicle in a woman is formed during embryonic life and is already present at birth, the age of the female egg is largely consistent with the age of the woman, although there are certainly cases where this is affected by other factors. However, the age of the mitochondria in most women’s eggs is the same as the age of the follicle, which is the same as the age of the woman. In this way, the older the woman is, the older the egg is, and the less energy she inherits to form an embryo, and the less potential for development. Second, chromosomes, the normal development of an embryo also depends on a normal genetic structure. Human genes are found in 23 pairs of chromosomes. An abnormal number of chromosomes can cause an embryo to not implant properly or develop into a normal fetus. It can also cause embryonic development to stop. When day 3 embryos are analyzed for chromosomes, studies have shown that only one-third of embryos have a normal number of chromosomes, and by the time they develop into blastocysts on day 5, there is a two-thirds chance that the blastocysts will have normal chromosomes, and embryos with abnormal chromosomes are eliminated naturally during the culture process.