title: The optimum number of oocytes in IVF treatment: an analysis of 2455 cycles in China.
abstract: OBJECTIVE
  What is the association between the number of oocytes retrieved and the live birth rate (LBR) following first IVF treatment cycles in China?
  
  
  CONCLUSIONS
  In first IVF treatment cycles, the LBR after fresh transfer was maximal in the groups with 6-10 or 11-15 oocytes and reduced in the groups with 0-5 or >15 oocytes. Despite this, the cumulative LBR after including frozen embryo transfer cycles increased with an ovarian response.
  
  
  BACKGROUND
  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.
  
  
  METHODS
  This is a large retrospective cohort study (n = 2455); patients were categorized into four groups according to the number of oocytes retrieved (0-5, 6-10, 11-15 and >15 oocytes). The fresh embryo 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.
  
  
  METHODS
  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.
  
  
  RESULTS
  The fresh embryo LBR per started cycle increased with the number of retrieved oocytes up to Groups 2 and 3 (6-10 and 11-15 oocytes) and then decreased, because of the high number of cycles with all embryos being cryopreserved, in order to avoid moderate-severe OHSS in group 4 (>15 oocytes). However, the cumulative LBR per started cycle continued to increase with oocyte number, as did the incidence of moderate-severe OHSS. There was no significant difference in the miscarriage rates among the patient groups.
  
  
  CONCLUSIONS
  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.
  
  
  CONCLUSIONS
  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.
  
  
  BACKGROUND
  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).
authors.affiliation: Center for Reproductive Medicine, Provincial Hospital Affiliated to Shandong University, National Research Center for Assisted Reproductive Technology and Reproductive Genetics, The Key Laboratory for Reproductive Endocrinology of Ministry of Education, Shandong Provincial Key Laboratory of Reproductive Medicine, 324 Jingwu Road, Jinan 250021, P.R. China and.
authors.forename: Jingjuan
authors.initials: J
authors.lastname: Ji
authors.forename: Yusheng
authors.initials: Y
authors.lastname: Liu
authors.forename: Xian Hong
authors.initials: XH
authors.lastname: Tong
authors.forename: Lihua
authors.initials: L
authors.lastname: Luo
authors.forename: Jinlong
authors.initials: J
authors.lastname: Ma
authors.forename: Zijiang
authors.initials: Z
authors.lastname: Chen
mesh_terms: D000022:Abortion, Spontaneous / Q000453:epidemiology; D000328:Adult; D002681:China; D004624:Embryo Transfer / Q000379:methods*; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods*; D006801:Humans; D016471:Ovarian Hyperstimulation Syndrome / Q000453:epidemiology; D011247:Pregnancy; D011256:Pregnancy Outcome; D012189:Retrospective Studies
keywords: in vitro fertilization; live birth rate; oocytes number; optimum; ovarian stimulation