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 development.

Design: Retrospective analysis of oocyte fertilization and embryo development 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 position were recorded during ICSI; fertilization was assessed on day 1; embryo development was evaluated on days 2 and 3.

Main Outcome Measure(s): Fertilization, embryo development, and implantation 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'clock polar-body orientation. Injections with the polar-body positioned at 7 or 11 o'clock result in the greatest number of high-quality embryos, significantly more than the adjacent 6 or 12 o'clock polar-body orientations and irrespective of oocyte anomaly frequency. Embryos originating from the 7 or 11 o'clock polar-body category implant at a higher rate, although the data are not significant.

Conclusion(s): The placement of the sperm during ICSI relative to the presumed 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.