Experience with subzonal insemination (SUZI) and intracytoplasmic sperm injection (ICSI) on unfertilized aged human oocytes

Abstract

The aim of this study was to assess the fertilizability of unfertilized aged human oocytes from failed in vitro fertilization (IVF) cycles using SUZI and ICSI. A total of 363 oocytes which showed no fertilization after conventional IVF was subjected to assisted fertilization using SUZI or ICSI. The microinjected oocytes which were derived from 72 patients undergoing their first IVF treatment had an intact polar body and no signs of degeneration. SUZI was carried out in 265 oocytes and ICSI in the remaining 98. Significantly more oocytes were damaged after ICSI (9 vs 0.3%, P < 0.01). Normal fertilization rates were higher at 24 hr in both groups and occurred more frequently after ICSI, although the difference did not reach statistical significance. Abnormal fertilization occurred significantly more often after SUZI at 48 hr (P < 0.005), but not at 24 hr. Cleavage rates were significantly higher after ICSI (94.4 vs 57.1%, P < 0.025) at 24 hr, but this was not observed at 48 hr, although the ICSI group still showed better cleavage rates (33.3 vs 19.1%). There was no difference in embryo quality in either group. Our results indicate that micromanipulation rather than reinsemination should be carried out on unfertilized human oocytes from failed IVF attempts. Both techniques can be used to achieve fertilization which occurs more often after ICSI. However, the trauma from the former technique on the microinjected oocytes may impair the potential of the generated embryos to achieve pregnancy compared to SUZI. Prospective randomized trials are necessary to address the problem.