A short discussion about how the ovary works to will give some understanding about the importance of getting the right egg. The ovary contains lots of eggs, about 1 to 2 million eggs at birth, around 400,000 eggs at puberty and loses about 1,000 eggs each month.
Of the thousand eggs that die every month, maybe 5-50 at any one time, will be in a state that allows them to respond to the body's hormones. These eggs all begin to grow, and the egg that is the most competent is the only one released. "Most competent" egg means that egg that is the best able to perform all the tasks required, compared with all the others around at that time.
The eggs grow in little pouches of fluid in ovaries called follicles (or cysts). The ovary has internal workings to choose the follicle with the most competent egg to grow and mature during the natural cycle in the human species. This means - Of all the eggs around at the time that might respond to the body's hormones, the body chooses the best egg available.
This is important, because we have already learned that women don't end up having a baby every month they have sex in cycles where they have produced an egg. It means that there are times where even though the body has chosen the best egg available, those eggs simply aren't good enough to make a baby. In fact, we now know that this is what happens most of the time. This is normal for humans.
Using FSH as part of IVF treatment interferes with this process. Eggs that the body wouldn't use because those eggs are abnormal (won't produce a baby) are also forced to mature. We have very small structures in each of our cells called chromosomes. Chromosomes are our genetic code, the software that runs our cells and ultimately our body. During the egg and sperm development process, half of our parents' chromosomes are lost (otherwise we would have too many).
Well then, why do we give hormones to produce more than one egg in a cycle? A good question, and the answer is that there are women who come in for fertility treatment that might produce more than one egg in a cycle that can result in a baby. These are women whose partners may have sperm problems, and the women are normally fertile. Results from published data do show that some hormone stimulation causes more babies to be born compared with no stimulation. But what it is about is getting things "just right". By just right, we mean, getting the most number of babies for the least number of eggs. It seems that collecting around five eggs achieves this.
Why is this? The hormone used to stimulate ovaries, called FSH, has been shown to affect the egg growth process. As the dose of FSH increases, it interferes with the ability of chromosomes to come together and split again within the cells of any resulting embryos. This causes abnormalities that prevent the embryo from forming into a healthy child. Therefore, higher doses of FSH not only increase side effects, but appears that it decreases how well eggs work.
The mild ovarian stimulation approach or MOS causes less interference with normal ovarian function and egg maturing. We know it produces better quality eggs as the retrieval of a modest number of oocytes following MOS is associated with a higher pregnancy rate when compared with patients using conventional stimulation where the same number of eggs is retrieved. With MOS therefore women end up using less drugs, having less side effects, less transfers, less emotional drain, taking less time and still end up having the SAME number of babies.
Nice option to consider, isn't it?