The relationship between controlled ovarian stimulation protocol, meiotic spindle visibility, position of the meiotic spindle relative to the polar body in the human oocyte, and clinical outcomes following ICSI

Purpose: To investigate the effects of different controlled ovarian stimulation (COS) protocols, including the progestin-primed ovarian stimulation (PPOS), long, short, and the gonadotropin-releasing hormone antagonist protocols, on meiotic spindle visibility and position within the oocyte and clinical outcomes following ICSI.

Methods: Before ICSI, spindle position (θ) just below the polar body (PB) was defined as 0° and categorized as follows: θ = 0°, 0° < θ ≤ 30°, 30° < θ ≤ 60°, 60° < θ ≤ 90°, 90° < θ ≤ 180°, between the PB and the oolemma, and nonvisible. The clinical outcomes after ICSI were retrospectively analyzed.

Results: The normal fertilization rate was significantly higher in oocytes with visible spindles than in oocytes with nonvisible spindles after each COS protocol, but did not differ based on spindle positioning (0° ≤ θ ≤ 180°). The rates of pregnancy, live birth/ongoing pregnancy, and miscarriage did not differ based on spindle visibility or positioning. In multinominal logistic regression analysis, female age was associated with spindle position, and the odds of a spindle located at 30° < θ ≤ 60°, at 60° < θ ≤ 90°, or at 90° < θ ≤ 180° were increased relative to θ = 0° in older women (odds ratio; 1.020, 1.030, and 1.060, respectively; p < 0.05).

Conclusion: Meiotic spindle positioning in the oocyte does not affect normal fertilization, blastulation, pregnancy, live birth/ongoing pregnancy, and miscarriage after ICSI, independent of the COS protocol used.