title: Optimum oocyte retrieved and transfer strategy in young women with normal ovarian reserve undergoing a long treatment protocol: a retrospective cohort study.
abstract: OBJECTIVE
  This study aimed to investigate the relationship between the number of oocytes retrieved and clinical outcomes in young women with normal ovarian reserve who were undergoing their first in vitro fertilization and embryo transfer (IVF-ET) cycle. The transfer strategy based on yielded oocytes was also discussed in this article.
  
  
  METHODS
  A total of 1567 patients who underwent first long protocol of IVF treatment in our reproductive medical center between January 2010 and June 2014 were categorized into five groups based on the retrieved oocyte number, namely, 4∼6, 7∼9, 10∼12, 13∼15, and ≥16. Baseline parameters were similar among the groups. Primary outcome was defined as the cumulative live birth rate (CLBR), and secondary outcomes included the rate of patients with high risks for ovarian hyperstimulation syndrome (OHSS).
  
  
  RESULTS
  It was found that the CLBR increased with the number of oocytes, as well as the rate for high risks of OHSS. In fresh cycles, 10∼12 oocyte group demonstrated the highest implantation rate (53.32 %), clinical pregnancy rate (CPR) (73.13 %), and live birth rate (LBR) (61.14 %), with no significant differences. Moreover, both cumulative CPR (CCPR) and CLBR became significantly higher in the 10∼12 oocyte group, compared with 4∼6 and 7∼9 groups. However, when the retrieved oocytes increased to 13∼15 or ≥16, the cumulative results did not have a significant increase. Also, the high risk rate of OHSS was much lower in the 10∼12 group (11.53 %) than that in the 13∼15 group (29.97 %) and ≥16 group (77.30 %). Unconditional multivariate logistic regression analysis showed that when ≥10 oocytes were retrieved, the CLBR increased significantly (P < 0.01). When oocyte number exceeded 16, the CPR of frozen embryo transfer cycle was much higher than that of fresh cycle (P < 0.05).
  
  
  CONCLUSIONS
  For young women with normal ovarian reserve, retrieving 10∼12 oocytes might result in optimized pregnancy outcomes in a fresh cycle with low OHSS risk and would not compromise cumulative outcomes. When ≥16 oocytes were retrieved, a "freeze-all" embryo strategy might be preferable.
authors.affiliation: Reproductive Medical Center, People's Hospital of Zhengzhou University, 450003, Weiwu Road, Zhengzhou, Henan Province, People's Republic of China. chenyuanhui1119@163.com.|Reproductive Medical Center, Henan Provincial People's Hospital, 450003, Weiwu Road, Zhengzhou, Henan Province, People's Republic of China. chenyuanhui1119@163.com.
authors.forename: Yuan-hui
authors.initials: YH
authors.lastname: Chen
authors.affiliation: Reproductive Medical Center, People's Hospital of Zhengzhou University, 450003, Weiwu Road, Zhengzhou, Henan Province, People's Republic of China. xxhlf9@163.com.|Reproductive Medical Center, Henan Provincial People's Hospital, 450003, Weiwu Road, Zhengzhou, Henan Province, People's Republic of China. xxhlf9@163.com.
authors.forename: Xiao-hang
authors.initials: XH
authors.lastname: Xu
authors.affiliation: Reproductive Medical Center, People's Hospital of Zhengzhou University, 450003, Weiwu Road, Zhengzhou, Henan Province, People's Republic of China. wqian0920@163.com.|Reproductive Medical Center, Henan Provincial People's Hospital, 450003, Weiwu Road, Zhengzhou, Henan Province, People's Republic of China. wqian0920@163.com.
authors.forename: Qian
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Reproductive Medical Center, Henan Provincial People's Hospital, 450003, Weiwu Road, Zhengzhou, Henan Province, People's Republic of China. zhangshd@126.com.
authors.forename: Shao-di
authors.initials: SD
authors.lastname: Zhang
authors.affiliation: Reproductive Medical Center, People's Hospital of Zhengzhou University, 450003, Weiwu Road, Zhengzhou, Henan Province, People's Republic of China. 15896513978@163.com.|Reproductive Medical Center, Henan Provincial People's Hospital, 450003, Weiwu Road, Zhengzhou, Henan Province, People's Republic of China. 15896513978@163.com.
authors.forename: Li-le
authors.initials: LL
authors.lastname: Jiang
authors.affiliation: Reproductive Medical Center, Henan Provincial People's Hospital, 450003, Weiwu Road, Zhengzhou, Henan Province, People's Republic of China. luckyzcl@qq.com.
authors.forename: Cui-lian
authors.initials: CL
authors.lastname: Zhang
authors.affiliation: Reproductive Medical Center, Henan Provincial People's Hospital, 450003, Weiwu Road, Zhengzhou, Henan Province, People's Republic of China. 1150789073@qq.com.
authors.forename: Zhao-jia
authors.initials: ZJ
authors.lastname: Ge
mesh_terms: D000328:Adult; D001723:Birth Rate; D015331:Cohort Studies; D015925:Cryopreservation / Q000379:methods; D004624:Embryo Transfer / Q000379:methods; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods*; D006801:Humans; D050498:Live Birth; D054315:Oocyte Retrieval / Q000379:methods*; D016471:Ovarian Hyperstimulation Syndrome / Q000209:etiology; D065851:Ovarian Reserve / Q000502:physiology*; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies; D016896:Treatment Outcome
keywords: Cumulative live birth; Normal ovarian reserve; Oocyte number; Ovarian hyperstimulation syndrome