Does meiotic spindle normality predict improved blastocyst development, implantation and live birth rates?

Objective: To investigate the relationship between spindle normality and: 1) blastocyst formation; 2) implantation rates; and 3) live birth rates.

Design: Prospective observational study.

Setting: A private fertility clinic.

Patient(s): One hundred patients ≤40 years old undergoing intracytoplasmic sperm injection (ICSI).

Intervention(s): Meiotic spindles were imaged before ICSI with the use of Oosight microscopy. With the use of specific criteria, spindle normality was independently assessed by two researchers. Blastocysts were chosen for transfer by standard light microscopic morphologic criteria by researchers who were blinded to the spindle assessment.

Main Outcome Measure(s): 1) Blastocyst formation; 2) implantation; and 3) live birth rates.

Result(s): A total of 808/920 oocytes were metaphase II. Of those, 711 (88%) had a visible spindle: 205 (29%) were normal spindles (NS) and 506 (71%) abnormal spindles (AS). Fertilization rates were significantly higher in NS oocytes. Although NS and AS oocytes both formed morphologically good-quality blastocysts, implantation and live birth rates were higher from NS oocytes. All ongoing pregnancies resulted from NS oocytes.

Conclusion(s): Spindle assessment with polarized light microscopy provides an early predictor of the pregnancy potential of that oocyte. AS oocytes can form good-quality blastocysts, but these appear to have little chance of live birth. Therefore, spindle assessment should improve the selection of the best embryo for single embryo transfer.