Sperm deposition site during ICSI affects fertilization and development

Objective: To evaluate the effects of sperm placement during ICSI relative to the M-II spindle location on fertilization and preimplantation developme nt. Design: Retrospective analysis of oocyte fertilization and embryo developme nt with respect to sperm deposition site during ICSI. Setting: A program of IVF-ET. Patient(s): Seven hundred seventy-six patients. Intervention(s): Egg quality, sperm deposition site, and polar-body positio n were recorded during ICSI; fertilization was assessed on day 1; embryo de velopment was evaluated on days 2 and 3. Main Outcome Measure(s): Fertilization, embryo development, and implantatio n rates. Result(s): Normal fertilization is not affected by polar-body orientation, with the exception of a significantly lower fertilization rate from a 9 o'c lock polar-body orientation. Injections with the polar-body positioned at 7 or 11 o'clock result in the greatest number of high-quality embryos, signi ficantly more than the adjacent 6 or 12 o'clock polar-body orientations and irrespective of oocyte anomaly frequency. Embryos originating from the 7 o r 11 o'clock: polar-body category implant at a higher rate, although the da ta are not significant. Conclusion(s): The placement of the sperm during ICSI relative to the presu med location of the meiotic spindle significantly impacts fertilization and high-quality embryo development. Sperm deposition in the M-II spindle area should be avoided. It appears that development, and not fertilization, is improved by decreasing the distance between the sperm cell and the spindle. (C) 1999 by American Society for Reproductive Medicine.