Polarization Microscopy Imaging for the Identification of Unfertilized Oocytes After Short-term Insemination

Objective: To develop a unique approach using polarization microscopy (PM) to determine whether the presence of a spindle can be used as an indicator associated with fertilization failure 5 hours after short-term insemination.

Design: Observational study.

Setting: Assisted reproduction center.

Patient(s): Eighty-five patients undergoing short-term insemination.

Intervention(s): Oocytes imaged via PM at 4, 5, and 6 hours after standard insemination.

Main Outcome Measure(s): Spindle visualization and fertilization rate, with rescue intracytoplasmic sperm injection (ICSI) results determined by rates of normal fertilization, abnormal fertilization, and good-quality embryo formation.

Result(s): After standard insemination, comparisons of spindle visualization at three time points indicated that the predictive accuracy rates were 84.30% at 5 hours, 86.80% at 6 hours, and 62.20% at 4 hours, with the rates at 5 and 6 hours statistically significantly higher than at 4 hours. A spindle was present in 242 of the 788 metaphase-II oocytes 5 hours after insemination, and there were 204 failed fertilizations on day 1. The positive predictive value was 0.84. After rescue ICSI, the abnormal fertilization rate of the polar body group (assessed using the polar body visualization method) was statistically significantly higher than that of the PM group (assessed using the spindle visualization method) and the regular ICSI group (9.37%, 5.88%, and 4.87%, respectively).

Conclusion(s): The presence of a spindle 5 hours after insemination in in vitro fertilization is an accurate indicator of unfertilized oocytes. Spindle imaging combined with rescue measures effectively prevents fertilization failure and decreases the polyspermy rate.