Abstract
ProposeThe presence of metaphase II (MII) spindle together with the polar body (PB) indicates completion of oocyte maturation. This study was designed to explore if spindle imaging can be used to optimize timing of intracytoplasmic sperm injection (ICSI).MethodsThe study involved 916 oocytes from 234 conventionally stimulated ICSI cycles with an unexpectedly poor ovarian response. All PB-displaying oocytes were subjected to polarized light microscopy (PLM) prior to ICSI. When MII spindle was absent in the majority of oocytes, ICSI was postponed and performed after additional spindle imaging. Fertilization, embryo development, and clinical outcome were evaluated with respect to the observed spindle pattern.ResultsThe visible spindle was absent in 32.64% of PB-displaying oocytes. The late-maturing oocytes extruding PB in vitro were less likely to exhibit a spindle signal than in vivo matured MII oocytes (38.86% vs. 89.84%). When fertilization was postponed, 59.39% of initially spindle-negative oocytes developed detectable MII spindle. Spindled eggs had significantly higher developmental potential, and the presence of the spindle has been identified as an independent measure for predicting the formation of the blastocyst. Embryos derived from spindle-positive oocytes also showed a higher chance to implant and develop to term. Notably, 11 children were conceived by finely timed fertilization of late-maturing oocytes which are normally discarded.ConclusionsThe study confirms the prognostic value of spindle imaging and demonstrates that immature oocytes can be clinically utilized and give rise to live births when the timing of ICSI is adjusted to their developmental stage.
Highlights
Oocyte maturity is an essential prerequisite for its successful fertilization and the viability of the resulting embryo
polar body (PB)-displaying oocytes are subjected to intracytoplasmic sperm injection (ICSI) while germinal vesicle and metaphase I (MI) oocytes are typically discarded
If the majority of oocytes within the treatment cycle was found to lack metaphase II (MII) spindle signal, ICSI was deliberately rescheduled to a later time (Supplementary Table 1)
Summary
Oocyte maturity is an essential prerequisite for its successful fertilization and the viability of the resulting embryo. It is customary to assume that each oocyte. Avoiding untimely intracytoplasmic sperm injection (ICSI) is important in the population of poor/slow responders with a low number of eggs available for fertilization. PB-displaying oocytes are subjected to ICSI while germinal vesicle and metaphase I (MI) oocytes are typically discarded. Immature oocytes, which spontaneously extruded PB in vitro, have been successfully used in fertility treatment [6,7,8,9,10]. Cumulative evidence suggests that the developmental potential of late-maturing oocytes could be better
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