Obstetrics, Gynecology and IVF Specialist Op.Dr.Numan Bayazıt gave important information on the subject. In fact, every person is born with 1 sperm and egg. Then why is the number of eggs so important in IVF? Because the probability of a healthy pregnancy in a human egg is very low compared to other living things in nature. Perhaps this is why a girl is born with several million eggs. A woman ovulates an average of 400 times after the first menstruation until menopause, but the probability of pregnancy at each ovulation is not more than 25%, even for the young age. In other words, only one out of 4 couples who want a child every month can get pregnant. After the forties, this probability drops below 5%. There is also the possibility of pregnancies resulting in miscarriage. While the probability of a pregnancy ending with a miscarriage is around 15% at young ages, it increases with age.
The main reason for all this is that not every egg is genetically normal. This situation has been understood by the genetic analyzes performed on the eggs during IVF applications. The probability of eggs being genetically normal decreases with age. While 35-10 out of 6 mature eggs taken from a 7-year-old woman are normal, this figure drops below 40 at 5 years old. It is necessary to obtain 44-8 eggs to come across a 10-year-old normal egg.
In a woman's normal cycle, 1 egg matures and hatches every month. If IVF had been done without any medication, the probability of pregnancy with this 1 egg would have been very low. For this reason, it is tried to increase the number of eggs while doing IVF. From the beginning of menstruation, injections are made and the growing eggs are followed by ultrasound. In fact, those seen on ultrasound are round fluid sacs. These are called follicles. Each follicle contains one egg. When the follicles are large enough, they are aspirated and the egg is searched for.
Op.Dr.Numan Bayazıt continues his words as follows;
From this stage onwards, it is better understood why a large number of follicles/eggs are desired. The probability of eggs coming from each aspirated follicle is around 80%. In other words, some of them are empty or the egg does not come. Not every egg that comes is mature. About 10-7 out of 8 eggs are of good quality to be used. Not all eggs are fertilized. Here, too, about 20% is lost. Not all fertilized ones divide and develop beautiful embryos. About half of the fertilized eggs stop at some stage of their development. Not every embryo that grows up to the stage we call blastocyst, which is apparently of good quality and transferred, cannot adhere. On average, one of 2-3 has the genetic structure to be able to conceive.
For all these reasons, it is a great advantage to have a good number of eggs during IVF. We can say that the ideal number is 12-13. However, a woman with a small number of eggs should not be discouraged. As a result, a pregnancy occurs with 1 quality egg. Especially before the age of 40, we have a high chance of conceiving even if there are few eggs. Especially after the age of 43, the quality of eggs decreases and their genetic structure deteriorates. In fact, at least half of the couples who apply to us have fewer eggs than desired and most of them are over the age of 40. In this case, we try to increase the probability of pregnancy by collecting eggs for a few months and making quality embryos as much as we can. This is called the pool system. In a sense, we are trying to eliminate the quality problem by increasing the number.