INFLUENCE OF OOCYTE PREINCUBATION TIME ON FERTILIZATION AFTER INTRACYTOPLASMIC SPERM INJECTION

During the intracytoplasmic sperm injection (ICSI) procedure, the coll ected oocytes are incubated until just before ICSI. The ideal preincub ation time of oocytes was investigated in 544 treatment cycles. Oocyte retrieval was carried out 35 h after human chorionic gonadotrophin ad ministration. Oocytes were cultured for between 1 and 11 h before ICSI . Embryo transfer was performed 48 h after oocyte collection. The surv ival, fertilization and cleavage rates of injected oocytes indicated n o statistically significant differences between oocytes preincubated f or different lengths of time. The proportion of good-quality embryos ( grades 1 and 2) was lower at 9-11 h of preincubation time than for all the other preincubation times (P < 0.001). No statistically significa nt differences were detected in the pregnancy rate between each group (mean: 15.9%), although the pregnancy rate at 9-11 h of preincubation time appeared to be low (7.7%), These results suggest that the oocyte retained sufficient potential for fertilization between 1 and 9 h afte r oocyte collection in ICSI, For the researchers who practise more com plex ICSI procedures than IVF, it would be convenient to be able to pe rform ICSI at any time between 1 and 9 h after oocyte collection.