[Unexpected failed fertilization in vitro: ICSI reinsemination or ICSI indication for subsequent cycles].

The objective was to determine if intracytoplasmatic sperm injection (ICSI) for "rescue" of unexpected failed conventional insemination should be carried out for therapeutic or diagnostic purposes, that is, as a predictor for performing ICSI as a standard treatment in subsequent cycles. A retrospective clinical study was carried in 26 patients who showed unexplained fertilization failure on a first conventional IVF attempt, and reinsemination by ICSI was performed. We compared these results with those of 13 of the 26 patients who underwent a second attempt in which ICSI was used as the only insemination technique. A fertilization rate of 46.27% was achieved with reinsemination by ICSI but none resulted in pregnancy (0%). Fertilization was achieved with ICSI in all patients with previous fertilization failure and a pregnancy rate of 38.46%. Patient characteristics, cycle characteristics, sperm parameters or oocyte quality did not differ significantly between two groups. In conclusion, the ICSI reinsemination technique can give good fertilization rates but the potential of the generated embryos to achieve pregnancy seems to be low. In addition, it can be demonstrated that these patients have good possibilities of obtaining a pregnancy in a following cycle using ICSI.