The quality of the eggs is one key factor when it comes to achieving pregnancy. The woman’s age is also crucial so that the eggs produced are of good quality.
Ever since the moment of birth a girl has all her eggs (although they are not mature), which means that, as time goes by, the quality of the eggs will worsen (from 35 years on) and there will be less quantity of them.
When it comes to ovarian reserve, the quantity of primordial follicles is analysed; this means the oocyte-containing structures that still have to mature and become eggs. The ovarian reserve means the quantity and quality of the eggs. At the time of birth a girl is estimated to have between 1 and 2 millions oocytes; when the woman begins having the period, she will have 400,000 oocytes, and at the age of 37 the ovarian reserve will have decreased to 25,000 oocytes. At the time of reaching menopause the ovarian reserve will count on less than 1,000 oocytes.
As this data demonstrate, the ovarian reserve decreases with the age of women: as they grow older the quantity and quality of eggs is reduced. However, this is not the only factor, some genetic and immunological system diseases, as well as bad habits, can have a negative impact causing what is known as premature menopause or premature ovarian failure (POF).
Calculation of the ovarian reserve
The quality of eggs is of vital importance to female fertility. Several studies show that the quality of the eggs is the main factor when it comes to achieving a good quality embryo, approximately 80%. When the ovarian reserve decreases this provokes female infertility and causes many complications when it comes to achieving pregnancy naturally.
In order to find out the ovarian reserve a common blood analysis is enough. The levels of several hormones are measured on the third day of the menstrual cycle, such as the follicle-stimulating hormone (FSH) and estradiol, whose high levels indicate a low egg production. The antimüllerian hormone (AMH) is also a good indicator of the ovarian reserve. Furthermore, it doesn’t depend on the menstrual cycle, so it can be analysed any day. Another test is the ultrasound of the female reproductive system, which allows the doctors to find out the quantity of follicles and eggs that the woman has.
However, the best way to find out the ovarian quality, which means if the follicles are able to mature and develop properly, is through an IVF process, since it allows the direct observation of the eggs and the embryos that they produce. After a process of ovarian stimulation the gynaecologist counts how many good size follicles (14 – 18mm) have developed properly. These follicles will be the ones stabbed during the follicular puncture to recover the eggs. The quality is then analysed in the laboratory, they must be rounded and the cytoplasm must be uniform. The eggs must be at the stage of metaphase II. In order to find this out, it must be checked whether the extrusion of the first polar body has taken place or not, by observing the limit of the cells in the zona pellucida that covers the oocyte.
Addiction to certain drugs and alcohol consumption alter and decrease the quality of the eggs, whereas a proper nutrition and healthy habits help improve ovarian reserve. The body mass index (BMI) plays also a vital role, since women with anorexia or overweight show alterations in ovulation.