Good ovarian response is associated with a higher birth rate regardless of whether the cycle makes use of fresh or frozen embryos
Various registries show that the cumulative live birth rate in assisted reproduction increases gradually and continuously in correlation with the number of oocytes obtained, and peaks when 10 to 15 oocytes are obtained. Beyond this number, the rate stabilises and begins to decline.
However, these figures are based solely on the response to ovarian stimulation shown by women undergoing their first fresh IVF cycle, and take no account of the possibilities offered by oocyte and embryo cryopreservation techniques.
A large multicentre study, conducted by Dr. Nikolaos Polyzos, clinical and scientific director of the Reproductive Medicine Service at Dexeus Women's Health reviewed the response to hormonal ovarian stimulation in a large sample of more than 14,469 women from 15 reference hospitals who were monitored for at least two years after undergoing either IVF or ICSI using either fresh or cryopreserved embryos.
Findings showed that the cumulative birth rate exceeded 70% when a total of 25 or more oocytes were obtained, with no stagnation beyond this number. Taking into account only fresh cycles, 13 oocytes was considered the optimal number, since the chances of achieving a live birth exceeded 36% in this case. While no significant decrease was observed with oocyte counts of more than 20, a decrease was subsequently observed probably because, beyond this, oocytes tend to be frozen and fewer fresh cycles are performed.
The findings of this study are based on a retrospective data analysis, and while there may be some level of bias, they show that ovarian stimulation performed in assisted human reproduction is unlikely to negatively impact the quality of the oocytes or embryos obtained, whether in fresh cycles or after cryopreservation.
Session 48: Outcomes and ovarian stimulation
Presentation: Cumulative live birth rates following the first ovarian stimulation for IVF/ICSI. A European multicenter analysis of ~15.000 women using individual patient data
Speaker: Polyzos Nikolaos P.
Clinical and Scientific Director of the Reproductive Medicine Service, Department of Obstetrics, Gynaecology and Reproductive Medicine, Dexeus University Hospital, Barcelona, Spain