Fertilization, which means that a new life is about to be born, is a very complex process, which also includes a series of processes such as sperm and egg recognition, sperm penetration of cumulus cells, sperm and egg fusion, and egg activation.
As long as there are abnormal factors, it can cause fertilization difficulties, because fertilization is the most basic and important step in IVF**, which is the result of the joint efforts of sperm and egg, and any abnormal factors may lead to fertilization failure.
Why does fertilization fail?
1. Egg factor.
1) Zona pellucida defects.
The zona pellucida is a layer of transparent tissue that wraps around the outside of the egg, which we can also compare to the shell of an egg. Whether the egg shell is too thick or too hard, the sperm will not penetrate, and generally speaking, the thickness of the zona pellucida is 175um, if it has exceeded a certain amount, it will make fertilization difficult. Also, if the gene of the zona pellucida is mutated, then the acrosome of the sperm will not be able to react with the zona pellucida, eventually leading to fertilization failure.
2) Oocyte abnormalities.
There is no obvious abnormality in the cytoplasm, polar body, and zona pellucida of the egg, and various mechanisms also play a very important role in the egg, and all egg growth and development may affect fertilization, so it is not possible to rely on one aspect to explain why fertilization fails.
3) Abnormal maturity.
The co-maturation of the nucleus and cytoplasm of the egg is a necessary condition for fertilization, and if the two do not mature together, the eggs cannot be fertilized normally, regardless of whether the eggs are different or not.
4) Oocyte activation failure.
The mature egg is in a quiet state, the metabolism is not as active as other eggs, after the successful fusion of the sperm and egg, the egg will be inducted accordingly in an instant, if it is not successfully activated, then the subsequent fertilization will not be successful.
2. Sperm factor.
In the early stage of IVF development, many people blame the quality of the egg for the failure of fertilization, and with the change of time, more scholars have found that a good sperm is particularly important in the process of fertilization, and the problem of sperm is because the number of sperm is not enough and the quality is not good.
Whether it is insufficient sperm count or poor sperm quality, it is difficult to conceive naturally, and artificial help is often needed to successfully fertilize. There may also be acrosome defects in some sperm, which causes the sperm to have no reaction to the egg, so the failure of egg activation is related to the defect of sperm-egg fusion, and sometimes it is directly related to the quality of sperm.