Manytest-tube families will have this question: Why do I have a lot of egg books, but I end up with the same number of embryos? I have so many D3 embryos, how can I only develop two blastocysts... In fact, as long as I understand the "layer by layer screening" during the embryo culture process, I can view this result with a more peaceful and rational attitude without having to be overly anxious.
,--,.This is not that there is a problem in a certain link, but that every step from egg maturation, sperm and egg fertilization to embryo development is undergoing natural and strict screening, and there may be normal losses at every step.
Not all the eggs taken out are "qualified players", and maturity is the first hard threshold.
The eggs that are retrieved aren’t all “qualified candidates” after all. Maturity is the first major criterion that needs to be met.Under natural conditions, women usually have only one egg that matures and discharges each month; the purpose of ovulation promotion in vitro babies is to allow more follicles to develop simultaneously, thereby obtaining more eggs. However, in the actual process, the development of these follicles The speed, shape and size are not exactly the same, and it is inevitable that some eggs will fail to meet the maturity standard.
Only mature eggs that have reached the MII stage are capable of being fertilized. Immature eggs that are in the MI or GV stages, or those that have degenerated, cannot undergo normal fertilization.Generally speaking, the maturity rate of eggs after promoted expulsion is about 80%. That is to say, if 10 eggs are taken, about 8 eggs will meet the maturity standard, and the remaining 2 eggs will be screened out at this step.
Even if the eggs mature smoothly, it does not mean that all of them can be successfully fertilized.
,.Fertilization is a complex and precise process that requires the perfect cooperation of sperm and eggs. In the process of sperm-egg integration, problems at any link may lead to failed fertilization or abnormal fertilization-such as poor sperm quality, too thick or abnormal egg zona pellucida, or failed activation of oocytes.
,70%-80%.Assuming that 10 eggs are taken and about 8 mature eggs are mature, about 5-6 eggs will be successfully fertilized; if both couples have sperm quality problems, the fertilization rate will further decrease, and the number of fertilized eggs that can move on to the next step will also decrease accordingly.
Successful fertilization is only the first step in the formation of an embryo. The subsequent development process is the most stringent test of the potential of the embryo.
,,,.Although some fertilized eggs successfully form dual pronuclei, they may not be able to start the cell division process normally, or may be stagnant early in development and eventually be naturally eliminated.
From the development of the fertilized egg until the blastocyst stage at day 3, the normal cleavage rate is approximately 50%-70%. If it needs to be cultured until the blastocyst stage at day 5-6, the challenges become even more stringent. The success rate of blastocyst formation varies significantly among individuals, ranging from 20%-50%.Simply put, 10 fertilized eggs may only produce 1-5 blastocysts, which is a normal development loss.
For test-tube families, the age of a woman is a key variable affecting embryo formation, especially after the age of 35, this effect will become more obvious.
,,35,.As we age, the quality of eggs will gradually decrease, and the probability of chromosomal abnormalities will also increase significantly, which will directly affect the fertilization rate and the normal development potential of the embryo.
For young women under 35 years of age, if they retrieve 10 eggs, they typically can obtain 3-5 blastocysts or 1-3 viable embryos. However, for women over 38 years of age, due to the decline in egg quality, the number of viable embryos available is likely to be significantly reduced. In some cases, it may even be impossible to create any blastocysts at all.
In addition to the quality of the eggs and sperm themselves, the conditions and technical operations of the embryo laboratory will also indirectly affect the final number of embryos.
,,.The development of embryos requires extremely high environmental requirements. The temperature, humidity, stability of medium components, and the accuracy of the embryologist's operation are all directly related to whether the embryo can grow normally.
A professional and skilled laboratory team can create the optimal environment for embryo development, thereby effectively reducing the number of embryos that are lost during the process. On the other hand, if the laboratory conditions do not meet standards, or if there are any deviations during the operation, it can lead to abnormal embryo development, further reducing the amount of usable embryos available.
,,.For example, patients with polycystic ovary syndrome often have a large number of eggs removed, but the quality of the eggs is uneven, and the available embryo rate is relatively low; while women with impaired ovarian reserve, even if a certain number of eggs can be removed, it may be because of the quality of the eggs itself, resulting in a decrease in the number of available embryos.
,,,.It is recommended to fully communicate with the attending doctor to understand your specific situation and allow the doctor to formulate follow-up treatment strategies that are more suitable for him. After all, the quality ofembryos is far more critical than the quantity on the road to assisted reproduction-a healthy high-quality embryo has a far higher chance of success than multiple low-quality embryos.