Complete oocyte activation failure after ICSI can be overcome by a modified injection technique

BACKGROUND: Complete fertilization failure after ICSI is a rare event, and it may happen repeatedly even in cases of normal sperm parameters and good ovarian response. In these cycles, alternative ICSI techniques may prove useful. METHODS: Our modified ICSI (mICSI) is characterized by aspiration close to the opposite membrane (the region of the mitochondria with a high inner mitochondrial membrane potential) which is followed by central deposition of the sperm. The method was applied prospectively to ICSI cycles of patients with a history of complete fertilization failure in previous ICSI cycles. In parallel, mICSI was compared with conventional ICSI in terms of further preimplantation development and treatment outcome. RESULTS: In patients with previous ICSI failures using conventional ICSI (no 2Pn zygotes out of 70 oocytes that had been injected) application of mICSI led to adequate fertilization (53.6%) and pregnancy rates (33.3%) (P<0.001; P<0.01). In patients without previous failed fertilization, no improvement in the rates of fertilization, blastocyst formation, implantation or clinical pregnancy could be seen. CONCLUSIONS: Our data indicate that the present version of ICSI is a reliable alternative to conventional ICSI. However, although it overcomes oocyte-dependent activation failure, routine application does not improve the overall results.