Outcomes of IVF at different time points of oocyte retrieval after injections of recombinant human chorionic gonadotrophin

Objective To explore the outcomes of IVF at different time points oocyte retrieval after injections of recombinant human chorionic gonadotrophin.Methods 204 cycles in infertility patients who had undergone vitro fertilization - embryo transfer ( IVF-ET ) and intracytoplasmic sperm injection ( ICSI ) during the period of May 2010 to January 2012 were selected.According to different time points of oocyte retrieval after injections of recombinant human chorionic gonadotrophin,the patients were divided into group of 34-36 hours ( control group,82 patients ) and group of 36-37 hours ( study group,122 patients ).Rate of oocytes retrieval,fertilization rate,M 11 egg ratio,cleavage rate,number of excellent embryos,and clinical pregnancy rate were analyzed retrospectively.Results Oocyte retrieval rate was ( 73.8 ± 20.5 )％ in the group of 34-36 hours and ( 78.9 ± 22.8 )％ in the group 36-37 hours,with a significant difference ( P＜ 0.05 ).M 11 egg ratio was ( 69.1 ± 21.3 ) ％ in the group 34-36 h and ( 73.7 ± 21.5 )％ in the group 36-37 h,with a significant difference ( P＜ 0.05 ).Fertilization rate was ( 73.3 ± 19.5 )％ in the group 34-36 h and ( 78.9 ± 22.1 )％ in the group 36-37 h,with a significant difference ( P＜ 0.05 ).Cleavage rate was lower in the group of 34-36 hour ( 88.3 ± 9.5 ) ％ than in the group of 36-37 hour ( 90.1 ± 9.8 ) ％,but with no significant difference ( P＞ 0.05 ); however,it trended to increase.The number of excellent embryos was lower in the group of 34-36 hours ( 3.9 ± 1.5 ) than in the group of 36-37 hours ( 4.2 ± 1.8 ),with no significant difference ( P＞ 0.05 ); but it trended to increase.The clinical pregnancy rate was lower in the group of 34-36 hours( 40.8％ )than in the group of 36-37 hours ( 42.9％ ),with no significant difference but an increasing tendency.Conclusions The oocytes retrieved rate,M 11 egg ratio,and fertilization rate are higer 36-37 hours after r-HCG injection than 34-36 hours.And the cleavage rate,number of excellent embryos,clinical pregnancy rate have a trendency to increase. Key words: Assisted Reproduction;  Recombinant human chorionic gonadotrophin;  Outcome of IVF