OBJECTIVETo determine an optimal insemination technique for unexplained infertility patients undergoing IVF or ICSI following failed intrauterine insemination (IUI).

METHODSSixty-five cycles of 61 patients with failed IUI were divided into four groups: Group A (37 cycles of IVF), Group B (19 cycles of ICSI), Group C (4 cycles of IVF and ICSI: half and half), Group D (5 cycles of ICSI after failed IVF). The conventional IVF cycles were defined as Group E (37 cycles), and the conventional ICSI cycles defined as Group F (24 cycles). The fertilization rate, completely failed fertilization rate, high quality embryo rate, clinical pregnancy rate and the implantation rate were compared among all the groups.

RESULTSThere were statistically significant differences in the fertilization rate, completely failed fertilization rate between Groups A and E (55.4% vs 72.8%, P < 0.05; 21.6% vs 0%, P < 0.005), and Groups A and B (55.4% vs 68.4%, P < 0.05; 21.6% vs 0%, P < 0.01). In Group D, there was statistically significant difference in the fertilization rate between IVF cycles and ICSI cycles (12.2% vs 74.2%, P < 0.005).

CONCLUSIONThe present study demonstrates that there may be 20% of totally failed fertilization in IVF cycles with unexplained primary infertility following failed IUI, and ICSI treatment can increase fertilization rate and avoid complete fertilization failure.