title: Fertilization and pregnancy potential of immature oocytes from stimulated intracytoplasmic sperm injection cycles.
abstract: OBJECTIVE
  We evaluated the fertilization potential of immature oocytes obtained from controlled ovarian hyperstimulation cycles of patients undergoing ICSI.
  
  
  METHODS
  We retrospectively analyzed 463 ICSI cycles containing at least one immature oocyte at oocyte denudation. ICSI was performed on mature oocytes at oocyte denudation (metaphase-II [MII] oocytes) and the oocytes that extruded the first polar body between oocyte denudation and ICSI (MI-MII oocytes). Fertilization and early embryonic development were compared between MII and MI-MII oocytes. To investigate the pregnancy potential of MI-MII oocytes, the pregnancy outcome was analyzed in 24 ICSI cycles containing only immature oocytes at retrieval.
  
  
  RESULTS
  The fertilization rate of MI-MII oocytes (37.0%) was significantly lower than that of MII oocytes (72.3%). The rates of delayed embryos and damaged embryos did not significantly differ. Eighty-one immature oocytes were retrieved in 24 cycles that retrieved only immature oocytes and 61 (75.3%) of them were in the MI stage. ICSI was performed on 36 oocytes (59.0%) that extruded the first polar body before ICSI and nine MI-MII oocytes (25.0%) were fertilized. Embryo transfers were performed in five cycles. Pregnancy was observed in one cycle, but it ended in biochemical pregnancy.
  
  
  CONCLUSIONS
  In ICSI cycles, oocytes that extruded the first polar body between denudation and ICSI can be used as a source of oocytes for sperm injection. However, their fertilization and pregnancy potential are lower than that of mature oocytes. Therefore, ovarian stimulation should be performed carefully for mature oocytes obtained at retrieval, especially in cycles with a small number of retrieved oocytes.
authors.affiliation: Laboratory of Reproductive Biology and Infertility, Cheil General Hospital and Women's Healthcare Center, Kwandong University College of Medicine, Seoul, Korea.
authors.forename: Seung Bi
authors.initials: SB
authors.lastname: Shin
authors.forename: Jae Won
authors.initials: JW
authors.lastname: Cho
authors.forename: Sun-Hee
authors.initials: SH
authors.lastname: Lee
authors.forename: Kwang Moon
authors.initials: KM
authors.lastname: Yang
authors.forename: Chun Kyu
authors.initials: CK
authors.lastname: Lim
authors.forename: Hyoung-Song
authors.initials: HS
authors.lastname: Lee
keywords: Immature oocytes; In vitro oocyte maturation, Fertilization; Intracytoplasmic sperm injection