The effect of repeated controlled ovarian stimulation cycles on the gamete and embryo development

The aim of this study was to investigate if there is an adverse effect of multiple controlled ovarian stimulation (COS) on the maturity of oocytes (MI and MII), fertilization rate, embryo developmental qualities and clinical pregnancy rates in donation cycles. In total, 65 patients undergoing oocyte donation cycles multiple times were included in this study. Patients were grouped as group A that consisted of donors with ≤2 stimulation cycles while B consisted of donors with ≥3 stimulation cycles; and group C included donors who had ≤15 oocytes, while group D had donors with ≥16 oocytes. Numbers of oocytes obtained, MI and MII oocytes, fertilization, embryo quality and clinical pregnancy outcomes were compared. Significant statistical differences were observed in total number of oocytes obtained, maturity of oocytes (MI and MII), fertilization rate, embryo qualities and clinical pregnancy outcomes of donors in groups A-D. Donors with ≤2 ovarian stimulation cycles had lower numbers of immature oocytes than donors with three or more stimulation cycles. However, donors with ≥3 stimulation cycles had higher numbers of mature oocytes, zygotes, with better day 3 embryo qualities and higher clinical pregnancy rates than donors with ≤2 stimulation cycles. Repeated COS does not seem to have any adverse effect on ovarian response to higher dose of artificial gonadotropin, as quality of oocytes collected and their embryological developmental potential were not affected by the number of successive stimulation cycles. The effect of multiple COS on the health of the oocyte donor needs to be assessed for future purpose.