Women are born with a finite number of eggs (1-2 million in both ovaries at birth) and at the time of puberty the total number decreases to approximately 500,000. At age 37, there are approximately 25,000 eggs left in the ovaries and less than 500 at the time of menopause. A monthly process of using up numerous eggs continues until the number of eggs remaining in the woman’s ovaries falls below a certain critical threshold, at which time ovarian function starts to decline and the woman becomes relatively resistant to ovarian stimulation with fertility drugs. Reduced ovarian responsivity to fertility drugs is usually the direct consequence of a decline in ovarian function. Egg quantity and quality are directly related to the woman’s age.
As a woman advances beyond 30 years of age, each mature egg is progressively less likely to be “normal” such that with every advancing year fertilization of her eggs is more likely to produce embryos with abnormal chromosome number and/or structure. Such abnormal embryos are referred to as being aneuploidic. As an example, at age 35 approximately 1 in 3 or 4 embryos are likely to be aneuploidic while at 40 yrs, aneuploidy affects about 80% embryos. At 43 years approximately 90% of embryos are so affected and at 45 years the incidence of aneuploidy could be as high as 95-100%.
Since it is nature’s intent to protect the integrity of the species through natural selection, abnormal embryos usually will fail to implant or attach to the uterine lining (In such cases the woman would probably not even be aware that she was actually pregnant for a very brief period of time) or be rejected in the first three months of pregnancy as a miscarriage. Infrequently, nature will make a mistake and allow a chromosomally defective fetus to continue on to delivery, resulting in a live birth (e.g. Down’s syndrome).
The risk of embryo aneuploidy increases with advancing age. This explains why there is a progressive increase in the incidence of infertility, miscarriage and birth defects that occur as the age of conception increases progressively. It also serves to explain why treatment of infertility (regardless of the chosen method) becomes progressively less successful with advancing maternal age.
A woman over 42 years would not only be far more likely to produce fewer eggs even following the administration of relatively high doses of fertility drugs, but a higher percentage of her eggs and embryos would be chromosomally abnormal because of her reproductive age. Accordingly, her chances of having a baby using her own eggs would be reduced. Conversely, a woman below 42 years of age undergoing in vitro fertilization, might yield many more eggs/embryos, thus allowing for increased availability of eggs/embryos and thereby, the opportunity to select out more and better quality embryos or blastocysts (advanced embryos grown for 5-6 days) for embryo transfer (ET). It should be pointed out that it is embryo/blastocyst quality rather than simply the number of embryos transferred to the uterus that influences the incidence of multiple pregnancies. Accordingly, the further the woman’s age has advanced beyond 42 years the greater the number of embryos or blastocysts (advanced embryos) that could be transferred safely to her uterus, without increasing the incidence of high-multiple pregnancies (triplets or greater number).
For women whose advancing age or ovarian resistance makes having a baby with their own eggs unlikely, Dr. Bayrak recommends ovum donation (using donated eggs from a younger person) as an excellent option to achieve a pregnancy in the shortest amount of time. Full term pregnancy or delivery rate with such a treatment option has been 60% per attempt with Dr. Bayrak’s experience.