During a woman’s menstrual cycle, a series of eggs begins a maturation process inside the ovaries but only the single best egg is ovulated. When an assisted reproduction cycle is performed at a fertility clinic, the ovaries undergo stimulation so that a high number of eggs develop.
“The day oocyte retrieval is performed, we collect the eggs that have been growing inside the follicles. They are obtained by inserting a needle into the follicle and using a suction device to aspirate the follicular fluid and cellular material including the oocyte, i.e. the follicle. The state of maturity of the oocytes cannot be ascertained until the follicles are peeled in the laboratory. Peeling consists in removing cells that surround the oocyte which provide the eggs with hormones so that they are able to reach maturation. Once the oocytes have been peeled, only those that are mature can be used, known in laboratory terminology as metaphase II oocytes.
Embryologists know that despite retrieving mature oocytes, there is no guarantee of the process being completed successfully as there are many anomalies associated with oocytes that affect the development of embryos that are created, meaning that fecundation cannot always proceed successfully.
Anomalies relating to oocytes include the following: large size which is usually indicative of chromosomal abnormalities, thickened zona pellucida (protective encapsulating shell), fragmented polar body or cytoplasm with inclusions or aggregations that have smooth endoplasmic reticulum.
Patients have often asked me how they can improve the quality of their eggs. Sometimes using a different stimulation procedure can produce oocytes of a moderately higher quality. A woman’s age is the most determining factor for both her ovarian reserve and the quality of her eggs.
Nagore informed us that there is no universal ranking for oocyte quality and that success rates are less linked to the morphological features of the eggs than the patient’s age. It is important that women know about egg vitrification, a treatment that enables them to preserve their fertility and keep the quality of their oocytes intact. This gives them the freedom to decide when it is the best time to become mothers.