The quality of the eggs is a very important factor in assisted reproduction treatments. Although the eggs are morphologically normal, this does not mean that the probability of pregnancy is 100%. However, it is possible to predict how the embryonic evolution will be, although other aspects must also be taken into account.
The three types of good quality egg markers are listed below:
- Gynecological indicators
- are mainly associated with the patient who comes to the human reproduction units and which are generally analyzed and assessed by the medical team: age, environment and ovarian reserve.
Age is the main indicator of egg quality. Numerous publications associate a greater risk of genetic abnormalities as the age of the patient increases. We should not confuse quality with ovarian reserve. For example, it could be the case that a 42-year-old woman presents a good ovarian reserve when the antral follicle count is analyzed by ultrasound and good levels of antimullerian hormone levels, but the oocyte quality will always be worse than that of a 30-year-old patient.
Another widely misused indicator is the antimullerian hormone values, which do not determine egg quality but rather egg quantity. Thus, in case a young patient has a low AMH, she has the possibility, despite obtaining a low number of oocytes, to be of good quality and therefore to carry a pregnancy to term.
Finally, the environment can greatly affect oocyte quality. We must understand that both unhealthy habits (tobacco, alcohol, drugs, etc.) and toxic habits to which we may be exposed, can directly or indirectly affect egg quality.
- Morphological indicators
- are established from the laboratory, once the oocyte extraction has taken place using puncture, they are characteristics that provide information, but they are not defining for the development of the embryonic evolution.
The process known as oocyte retrieval, allows us to analyze in first instance the Cumulus-Oocyte Complex (being the cumulus a group of cells closely related to the oocyte and that help its maturation) seeing if it is an immature oocyte, quantity of cells and their cohesion. Analyzing the cumulus-oocyte complex is important in conventional IVF procedures, to analyze the possible success of fertilization. In the case of sperm microinjection (ICSI) requires the decumulation, i.e. removing the cells that are around the oocyte, to check the optimum stage of maturity. Once decumulated we can see some cytoplasmic alterations such as granularity, smooth endoplasmic reticulum, vacuoles or inclusions; or extra-cytoplasmic alterations such as detritus in the perivitelline space, anomalies of the pellucid zone, increase in the perivitelline space or alterations of the first polar corpuscle.
As we have previously said, these are not characteristics that are harmful in all cases, but they do provide information and can explain the deficient embryonic evolution.
- Embryonic indicators
- are usually important to extrapolate the oocyte quality. In general, a worse oocyte quality is related to situations with anomalous fertilization or bad embryonic evolution during the first days of evolution, although it is true that at the moment in which the malefactor is added it is more difficult to predict exactly which factor is altering the embryonic development.