A woman who is over age 43 or 44 will often be turned away from any chance at assisted reproductive technology because of the age and therefore poor state of her ovaries. She may fail to respond as favorably to the gonadotropins as her younger counterpart, because her eggs have become less responsive to hormonal stimulation. She may produce few numbers of eggs, whose outer capsule is tougher and thus less capable of fertilization. Those eggs which do become fertilized may have more inclusions during early embryologic development, meaning there are more waste products put out by the mitochondria. Less make it to the blastocyst stage, even fewer are capable of implantation and fewer yet make it through the full embryonic development.
That is why a woman over forty is statistically less likely to give birth, and is encouraged to find
alternative ways of becoming a mother. She will be told she has poor quality eggs. Her reproductive endocrinologist will strongly suggest that she consider using a younger donor's eggs. This makes her chances of having a baby, and thus her RE's statistics, much higher.
The reason for the lower chances of assisted reproductive success in older women is because the only portion of the hormonal process that is manipulated is the last few weeks of this many months' process. Massive doses of gonadotropin hormones are given to the women in order to (hopefully) recruit more follicles. This doesn't, however, make them of better quality. Perhaps the reason she has been unsuccessful in conceiving in the first place is because her hypothalamic-pituitary-ovarian axis has been ailing, and the reflection has been in the resistance of her ovaries, the eggs contained within, and thus the inability to conceive. It seems that the older a woman is, this process of follicular development, which takes up the better part of a year, becomes more susceptible to breakdown.
Experience has shown that if the hormonal system is in perfect working order and a woman has clockwork menstrual cycles, no matter what her age, a healthy egg can be released on time. It then has a good chance of becoming fertilized, implanting, and making it through embryologic development to become a child.
The emphasis here is on the healthy hormonal cycle. If each individual element of the hypothalamic-pituitary -ovarian axis is still in healthy inter-relationship dring this process, the developing follicles are going to reflect this state of well-being.
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