Deciding between Egg and Embryo Banking for Fertility preservation (FP)

Women should not delay trying to have a baby, thinking that as long as they are ovulating regularly the biological clock can simply be put on hold or that they can simply to freeze their eggs and then later decide if/when to thaw them for use. The truth is that as a woman progresses to and beyond her mid-thirties, there is a steady and ever accelerating decline in the quality of their eggs that will inevitably impact her chance of having a baby. Not only will her chances decline over time, but so will the chance of a successful, healthy pregnancy. This is regardless of whether she tries to conceive without medical assistance, or following assisted reproduction (intrauterine insemination-IUI, in vitro fertilization-IVF, or following egg freezing. You see….as a woman ages beyond her mid-thirties the chance of any ovulated or harvested egg being chromosomally normal declines with the process accelerating rapidly as she advances to and beyond her 40’s. The result is a rapid reduction in conception rate and a rise in both miscarriages and chromosomal birth defects such as Down syndrome.

Consider the following statistics: At 30 years of age the natural conception rate per ovulation cycle is approximately 15-20%, the miscarriage rate…10-15% and the chance of a baby being affected by Down syndrome is but 1:1000. The comparable best-case scenario for conception following IVF rates is a 40-50% conception rate, an unaltered (10-15%) miscarriage rate and 1:1000 chance of Down syndrome while by age 45 years, the chance of natural conception per month of trying is probably <2%, the chance of miscarriage >60% and the risk of a baby having Down syndrome about 1:40. Following conventional IVF, the same woman of 45y would have about a 3-5% chance of having a baby, and the likelihood of miscarriage and having a baby with  Down syndrome would be 50-60% and 1:40 respectively. In fact, as recently reported from Australia, (and is probably similar for other 1st world counties too) where about 5% of babies born annually result from IVF, one out of three cycles initiated in women 25-34 years of age result in a live birth while at 45 years and above, < 1:100 initiated IVF cycles resulted in a live birth.

 

PREIMPLANTATION GENETIC SCREENING (PGS)- EMBRYO/EGG SELECTION:

Embryo karyotyping using PGS identifies all the chromosomes and allows selection of the most “competent” embryos (i.e., those that are highly likely to propagate a viable pregnancy), thereby dramatically improving the efficiency of IVF. As such it can be considered to be a virtual “game changer”! Not only does it vastly improve the baby rate per embryo transferred, but (regardless of the woman’s age) it also dramatically reduces the risk of both miscarriage and numerical chromosomal birth defects.

PGS by allowing for thorough embryo evaluation, offers major diagnostic and therapeutic advantages, especially in cases of “unexplained” recurrent IVF failure “unexplained” infertility”, recurrent pregnancy loss (RPL) and in older women who not only produce fewer eggs per stimulated IVF cycle, but whose eggs have a very much reduced chance of being chromosomally normal.

It is especially women over 39 years and those with diminished ovarian reserve (DOR) that can benefit from pre-implantation embryo/blastocyst biopsy with selective banking (stock-piling) of PGS- normal (“the most “competent) embryos over several cycles. Such selective embryo storage, in essence, diminishes the impact of a rapidly advancing biological clock, allowing such women to capitalize on whatever time is left…….so to say, to “make hay while the sun still shines”.

Egg Cryopreservation (freezing):  An egg is a single cell, and as such no matter how good the freezing process, it is far more vulnerable to being damaged than is a multi-cellular embryo. Furthermore, even in young women, only about 1 in 2 eggs are likely to be chromosomally normal. Thereupon, there is an invariable, steady age-related decline to less than 1 in 10 eggs by the time the woman reaches her mid-40’s. Combine the difficulty in safely freezing a single cell(egg) with the fact  that chromosomally abnormal eggs cannot propagate healthy babies and you will readily understand why even today,  the best one can hope for even in a younger woman (<35y) is that the chance that a frozen egg will ultimately propagate a normal live baby, is <8% . And, the older a woman becomes, the lower the chance of success will be …such that after age 40y it is <3% per egg. Contrast this with the baby rate following frozen blastocysts where the comparable success rate per embryo is usually 3-fold higher. However, when it comes to selectively freeze PGS-normal blastocysts, the success rate is between 40% and 50% per transferred blastocyst, regardless of the age of the woman. 

Given the adverse effect of advancing age on reproductive potential, women/couples seeking to initiate or expand their families should carefully consider their reproductive options before reaching 35 years of age. This should include adoption, assisted reproduction and IVF with fresh embryo transfer, versus freezing embryos or eggs for future dispensation. However, when embryo freezing is done, blastocyst selection using PGS, should be seriously considered.

When it comes to the choice of egg freezing, I would caution that the methods of egg selection currently in use, do not include karyotyping and thus subsequent results remain so poor and imprecise as to mandate careful deliberation. In my opinion, women over 35y should be cautioned and women over 40Y should be counseled against egg banking. I suggest that for such women embryo banking is a preferred approach.

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