🧬 Why does an embryo not develop from every egg?
Do you think that if 10 eggs are retrieved during the EKO process, 10 embryos will definitely be formed?
In reality, it is not guaranteed that every egg will turn into an embryo!
🔬 The path from egg to embryo: main reasons
There are several reasons for this:
Immaturity of the egg
Not all retrieved cells may be ready for fertilization. Only a mature egg can be fertilized.
Fertilization process
Some eggs do not fertilize with sperm, even in laboratory conditions.
Genetic factors
Chromosomal changes can affect embryo development. Such embryos often cannot continue to develop.
Developmental arrest
Some embryos do not continue to divide in the early days. The most frequent arrest is usually observed in the period from day 3 to day 5 of development.
How does the number of eggs decrease during the EKO process?
In embryology, this phenomenon is called "attrition": the number of cells naturally decreases at each stage. An approximate example:
- 10 eggs are retrieved;
- approximately 8 of them will be mature;
- approximately 70–80 percent of the mature ones will fertilize, meaning approximately 6 embryos will be formed;
- approximately 30–50 percent of the fertilized ones will reach the blastocyst stage, meaning approximately 2–3 embryos.
These are average, approximate indicators: the exact result depends on the patient's age, egg and sperm quality, and the laboratory.
Is this situation normal?
Yes. This process is considered a natural "selection": embryos that are genetically unsuitable for development usually stop on their own. Therefore, a decrease in the number of embryos is usually not a doctor or laboratory error, but a natural feature of human reproduction.
The important thing is quality, not quantity
What matters is not just the number of eggs, but also their quality and the developmental potential of the embryos.
How do age and sperm quality affect this?
As a woman's age increases, the probability of chromosomal changes in eggs rises, so the proportion of chromosomally normal embryos decreases. Sperm quality also affects fertilization and embryo development: in such cases, the ICSI method can be used to assist with fertilization.
Have you also wondered why embryos are not formed from all eggs? Leave your questions in the comments!
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📨 Source: Telegram: @eko_iksi_clinic