title: Embryonic development in human oocytes fertilized by split insemination.
abstract: OBJECTIVE
  To compare the laboratory outcomes of intracytoplasmic sperm injection (ICSI) and conventional insemination using sibling oocytes in poor prognosis IVF cycles where ICSI is not indicated.
  
  
  METHODS
  Couples undergoing IVF with following conditions were enrolled: history of more than 3 years of unexplained infertility, history of ≥3 failed intrauterine insemination, leukocytospermia or wide variation in semen analysis, poor oocyte quality, or ≥50% of embryos had poor quality in previous IVF cycle(s). Couples with severe male factor requiring ICSI were excluded. Oocytes were randomly assigned to the conventional insemination (conventional group) or ICSI (ICSI group). Fertilization rate (FR), total fertilization failure, and embryonic development at day 3 and day 5 were assessed.
  
  
  RESULTS
  A total of 309 mature oocytes from 37 IVF cycles (32 couples) were obtained: 161 were assigned to conventional group and 148 to ICSI group. FR was significantly higher in the ICSI group compared to the conventional group (90.5% vs. 72.7%, P<0.001). Total fertilization failure occurred in only one cycle in conventional group. On day 3, the percentage of cleavage stage embryos was higher in ICSI group however the difference was marginally significant (P=0.055). In 11 cycles in which day 5 culture was attempted, the percentage of blastocyst (per cleaved embryo) was significantly higher in the ICSI group than the conventional group (55.9% vs. 25.9%, P=0.029).
  
  
  CONCLUSIONS
  Higher FR and more blastocyst could be achieved by ICSI in specific circumstances. Fertilization method can be tailored accordingly to improve IVF outcomes.
authors.affiliation: Department of Obstetrics and Gynecology, Seoul National University Bundang Hospital, Seongnam, Korea.
authors.forename: Myo Sun
authors.initials: MS
authors.lastname: Kim
authors.affiliation: Department of Obstetrics and Gynecology, Seoul National University Bundang Hospital, Seongnam, Korea.
authors.forename: Jayeon
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Obstetrics and Gynecology, Seoul National University Bundang Hospital, Seongnam, Korea.
authors.forename: Hye Won
authors.initials: HW
authors.lastname: Youm
authors.affiliation: Department of Obstetrics and Gynecology, Seoul National University Bundang Hospital, Seongnam, Korea.
authors.forename: Jung Yeon
authors.initials: JY
authors.lastname: Park
authors.affiliation: Department of Obstetrics and Gynecology, Seoul National University Bundang Hospital, Seongnam, Korea. ; Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Hwa Young
authors.initials: HY
authors.lastname: Choi
authors.affiliation: Department of Obstetrics and Gynecology, Seoul National University Bundang Hospital, Seongnam, Korea. ; Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Byung Chul
authors.initials: BC
authors.lastname: Jee
keywords: Blastocyst; Fertilization; Fertilization in vitro; Intracytoplasmic sperm injection; Split insemination