Accumulation of oocytes from a few modified natural cycles to improve IVF results: a pilot study

Purpose To evaluate the role of co-transfer of embryos derived from vitrified oocytes accumulated during the previous modified natural cycles and an embryo developed from the last one as an alternative to repetitive single embryo transfer in a fresh modified natural cycle. Methods Thirty-six patients underwent ICSI procedure with three frozen natural oocytes supplemented by a fresh one obtained from the fourth modified natural cycle. Thirty-one controls received at least three consecutive single embryo transfer in a fresh modified natural cycle. Results In the study group the oocyte retrieval, survival and total fertilization rate were 73.0 %, 78.1 %, and 64.5 %, respectively. Fifty-two embryos were transferred in 29 transfers. In the control group the oocyte retrieval and fertilization rate was 77.4 % and 83.7 %, respectively. Fifty single embryo transfers were performed. Of a total 14 pregnancies obtained in the study group 10 were defined as clinical and 4 as abortions. In the control group a total of 8 single clinical pregnancies and 2 miscarriages were encountered. The overall (20.0 % vs 48.2 %) and the clinical (16.0 % vs 34.4 %) pregnancy rate were significantly higher in the study group having cumulative embryo transfer following the oocyte accumulation. Conclusions These data demonstrate that the co-transfer of embryos derived from vitrified oocytes accumulated during the previous modified natural cycles and an embryo developed from the last fresh modified natural cycle assure an excellent clinical outcome with the overall and clinical pregnancy rate significantly higher compared to the repetitive single embryo transfer in a fresh modified natural cycle.