Does Ovarian Stimulation For IVF Adversely Effect Embryo Implantation?
Egg donor treatment achieves very high success rates, with most clinics reporting live birth rates between 50 and 70%. These excellent success rates are largely explained by the fact that these eggs typically come from young fertile women in their 20’s. The reason that egg donation is the chosen treatment is most commonly that the intended mother has shown signs of diminished number and quality of eggs (diminished ovarian reserve). However, most clinicians have observed anecdotally that egg donation treatment success rates are superior to IVF success rates among young women who would also be expected to have excellent egg quality. It has long been suspected among clinicians that vigorous stimulation of the ovaries in standard IVF treatment creates an environment that is not ideal for embryo implantation. A large study out of Duke University published in the August 2014 issue of Fertility and Sterility (Yeh JS, Steward RG, Dude AM, et.al.), compared pregnancy rates among donor egg treatment cycles to IVF treatment cycles in which the intended mother used her own (autologous) eggs. They investigated whether there is in fact a difference in the pregnancy, implantation, and live birth rates comparing similarly matched groups.
The investigators carefully chose which autologous IVF patients would be used in the comparison, including only women 20-30 years of age, who had at least 10 eggs retrieved. It is well understood that one of the most important reasons for the high success of egg donation is the age of the donors and therefore the high quality of their eggs. The investigators wanted to determine if there was a difference the success rates comparing the two groups related to something other than the quality of the eggs. Toward this end, they also did not include any patients with a diagnosis that could affect the uterine environment such as PCOS, uterine factor, endometriosis or hydrosalpinx. The purpose of these exclusions was to make the two groups of patients being compared very similar, with the exception of the fact that the autologous IVF group underwent vigorous ovarian stimulation and removal of their eggs in the treatment cycle, and the egg donor group did not.
Significantly higher implantation, pregnancy, and live birth rates were observed in the donor egg group compared with the autologous group. Implantation, clinical pregnancy, and live birth rates were 49%, 68%, and 59% for the donor egg group and 42%, 59%, and 53% for the autologous group. The authors created multiple subgroups for comparison including intracytoplasmic sperm injection, unexplained infertility, prior tubal ligation, blastocyst transfer, etc. In every subgroup, higher success rates were noted in the egg donor group.
The results of this study suggest that the very high hormone levels present at the time of embryo transfer, in patients undergoing IVF with their own eggs, is detrimental to the implantation process. The fact that the improved success rates in the egg donor group was observed in every one of the subgroups of patients suggests that it is the high hormone levels generated in the autologous IVF group negatively affects outcomes. This study supports other studies that have suggested that the high estrogen environment created when the ovaries are stimulated for traditional IVF might be detrimental to embryo attachment to the uterine wall.
Freezing all embryos created in fresh IVF cycles, and transferring them at a later date in a controlled frozen embryo transfer cycle is being utilized in many centers in an attempt to eliminate the detrimental affects of the high estrogen environment on embryo attachment.