The optimum number of oocytes in IVF treatment: an analysis of 2455 cycles in China

What is the association between the number of oocytes retrieved and the live birth rate (LBR) following first IVF treatment cycles in China? In first IVF treatment cycles, the LBR after fresh transfer was maximal in the groups with 610 or 1115 oocytes and reduced in the groups with 05 or 15 oocytes. Despite this, the cumulative LBR after including frozen embryo transfer cycles increased with an ovarian response. There is a strong association between oocyte number and IVF outcome; however, this is a comprehensive analysis conducted to investigate the relationship between oocyte number and fresh cycle as well as cumulative LBRs in first IVF treatment cycles. This is a large retrospective cohort study (n 2455); patients were categorized into four groups according to the number of oocytes retrieved (05, 610, 1115 and 15 oocytes). The fresh embro transfer LBR and cumulative LBR were evaluated by group. Univariate analysis was performed to identify factors that predict the chance of LBR. Multivariate logistic regression was used to assess the association between oocyte number and LBR after adjusting for confounding factors that were identified as significant in the univariate analysis. A total of 2455 women who were undergoing their first IVF treatment cycle at the Reproductive Medicine Center of Anhui Provincial Hospital, P.R. China from April 2007 to December 2011 were identified and reviewed. All patients had normal menstrual cycles and were stimulated with a long GnRH agonist protocol. Associations between oocyte number and LBR and miscarriage rate as well as the rate of moderate-severe ovarian hyperstimulation syndrome (OHSS) were analyzed. The fresh embryo LBR per started cycle increased with the number of retrieved oocytes up to Groups 2 and 3 (610 and 1115 oocytes) and then decreased, because of the high number of cycles with all embryos being cryopreserved, in order to avoid moderatesevere OHSS in group 4 (15 oocytes). However, the cumulative LBR per started cycle continued to increase with oocyte number, as did the incidence of moderatesevere OHSS. There was no significant difference in the miscarriage rates among the patient groups. As a retrospective study, our analysis depends on previously recorded data; therefore, certain variables could not be collected. Our findings may be influenced by our young and thin patient population and the inability to control for certain markers of ovarian reserve such as historical maximum serum FSH, antral follicle count and serum anti-Mullerian hormone. Our data suggest that in IVF cycles stimulated with a long protocol, the optimal number of oocytes for achieving a live birth is somewhere between 6 and 15. The balance between maximum treatment success and minimum risk of complications, especially OHSS, should be further investigated. This study was supported by the Medical Scientific Research Plan Project of Anhui Provincial Department of Health (13ZC014) and the Natural Science Foundation of Anhui Higher Education Institutions (KJ2013Z132).