A comparative analysis of embryos derived from routine in-vitro fertilization and subzonal microinsemination

Embryos obtained from patients undergoing routine in-vitro fertilization (IVF) and embryo transfer were compared with those undergoing subzonal microinsemination (SUZI) for male factor infertility. Overall, the proportion of cleaved embryos was significantly higher in the IVF group in comparison with the SUZI group at 48 h post-insemination [1533 out of 1609 (95.3%) versus 776 out of 952 (81.5%)]. The mean +/- SD grading score of the IVF-derived embryos of 3.61 +/- 0.50 was significantly better than that for SUZI of 2.97 +/- 0.86 (P < 0.0005) at the same time. The implantation rates following the replacement of IVF or SUZI embryos at 48 h were comparable: 14.3 and 10.0% respectively. However, the IVF embryo implantation rate of 15.1% at 72 h was significantly better than that following the replacement of SUZI embryos at either 48 (10.0%) or 72 h (8.0%). The replacement of SUZI-derived embryos at 48 h resulted in significantly higher pregnancy (25.0%) and implantation rates (10.0%) than at 72 h, with rates of 10.8 and 8.0% respectively. Similarly, the overall embryo quality deteriorated following in-vitro culture for up to 72 h. The clinical pregnancy loss rate (33.0%) was highest following the replacement of SUZI embryos at 72 h, although the data were limited. It is suggested that these data indicate that a combination of in-vitro manipulation, the injection of multiple spermatozoa into the subzonal space and probably the genomic capacity of spermatozoa derived from poor-quality semen may contribute to the poorer outcome of embryo development following SUZI. Prolonged in-vitro culture beyond 48 h appears to be deleterious to the development of SUZI cleaved embryos and the subsequent outcome of treatment, and hence should be avoided.