title: Effects of cumulus cells removal after 6 h co-incubation of gametes on the outcomes of human IVF.
abstract: OBJECTIVE
  To investigate the effects of cumulus cells removal after 6 h co-incubation of gametes on the fertilization, polyspermy, multinucleation and clinical pregnancy rates in human IVF.
  
  
  METHODS
  A total of 1,200 IVF-ET cycles undergoing 6 h co-incubation of gametes in 2009 were included in this study. Inclusion criteria were: female age <38 years, first IVF treatment, with bi-ovary and normal ovarian response, e.g., 4 ~ 20 oocytes could be obtained. A 6 h period of co-incubation was applied in all IVF cycles. According to the history of infertility, cumulus cells were mechanically removed either 6 h post-insemination or 20 h post-insemination. For couples with primary infertility, or unexplained infertility, or mild oligospermia or asthenospermia, the cumulus cells were removed at 6 h of insemination for the polar body observation (6 h group, n = 565). Of these, 80 cycles received early rescue ICSI due to fertilization failure or low fertilization rate at 6 h of insemination. For couples with secondary infertility and normal semen analysis, the cumulus cells were removed at 20 h of insemination as routine (20 h group, n = 635). Of these, three cycles received late rescue ICSI due to fertilization failure at 20 h of insemination. Normal fertilization, polyspermy (≥3PN), multinucleation and clinical pregnancy rates were compared between the two groups (rescue ICSI cycles were not included in the comparison in both groups).
  
  
  RESULTS
  Significant difference (P < 0.05) was observed between the groups regarding polyspermy rates (7.48% in 6 h group and 9.22% in 20 h group). No difference was observed between the groups regarding normal fertilization rates (2PN rate) (64.89% in 6 h group and 65.74% in 20 h group). No difference was observed between the groups regarding multinucleation and clinical pregnancy rates (11.01% and 65.15% in 6 h group, 10.75% and 66.93% in 20 h group, respectively). The clinical pregnancy rate was 51.43% in cycles receiving early rescue ICSI, while no clinical pregnancy was obtained in cycles receiving late rescue ICSI.
  
  
  CONCLUSIONS
  The present results indicate that cumulus cells removal at 6 h of insemination is a relatively safe operation, which yielded comparable normal fertilization rate, multinucleation and clinical pregnancy rates compared with 20 h group. This protocol may be beneficial for early obsevation of fertilization failure and make early rescue ICSI possible.
authors: Chong Qing Reproductive and Genetics Institute, Chongqing Obstetrics and Gynecology Hospital, 64 Jing Tang ST, Yu Zhong District, Chongqing, 400013, China.
authors: Shun
authors: S
authors: Xiong
authors: Wei
authors: W
authors: Han
authors: Jun Xia
authors: JX
authors: Liu
authors: Xiao Dong
authors: XD
authors: Zhang
authors: Wei Wei
authors: WW
authors: Liu
authors: Hong
authors: H
authors: Liu
authors: Guo Ning
authors: GN
authors: Huang
mesh_terms: D000328:Adult; D054885:Cumulus Cells / Q000166:cytology / Q000378:metabolism*; D005260:Female; D005306:Fertilization / Q000502:physiology; D005307:Fertilization in Vitro / Q000379:methods*; D006801:Humans; D007246:Infertility / Q000628:therapy; D011247:Pregnancy; D018873:Pregnancy Rate; D020554:Sperm Injections, Intracytoplasmic / Q000379:methods; D013997:Time Factors