Abstract
Unfertilization after conventional IVF is confirmed by the existence of Metaphase-II (M-II) chromosome and first polar body. Spindle examination in unfertilized eggs using the polarization microscope is useful to assist rescue ICSI. However it has limitations since this apparatus observes only the existence of spindle not the stage of nuclear maturation (M-II, Anaphase-II or Telophase-II). Nomarski differential interference contrast microscopy clarifies each stage of second meiotic cell division. We performed this retrospective study to investigate the usefulness of this new improved technique. Retrospective cohort study for development of rescue ICSI. 425 Oocytes from 38 patients who agreed to participate in this study were observed 4 hours after insemination from January 2015 to December 2015. Unfertilized oocytes were identified by the normal width of chromosomes at M-II stage without extrusion of second polar body or white colored spindle with full length adjacent to the cytoplasmic membrane. Fertilized oocytes showed half width of chromosome in a line and shortening spindle 2-3 hours after the start of the fertilization (Anaphase-II). As fertilization was proceeding, M-II chromosomes became aggregated and divided into second polar body with spindle crossing the membrane 3-4 hours later. About 4 hours after insemination, second polar body extruded with remaining round M-II chromosomes and spindle was observed close to the perivitelline space (Telophase-II). 5-6 hours later small female pronucleus appeared just below the second polar body without the spindle. 1. The 425 freshly ovulated M-II oocytes were examined. The proportion of unfertilized oocytes that remained at M-II stage was 20.4% (87/425), fertilized oocytes after completion of second meiosis was 79.5% (338/425). 2. The fertilization, cleavage, blastocyst stage rates, pregnancy and miscarriage rates in fertilized oocytes (A) and unfertilized oocytes followed by new rescue ICSI (B) are listed in Table. No 1PN or 3PN oocytes could be observed both in group A and B. Not all of M-II oocytes could be identified as having completed second meiosis after insemination. Some chromosomes were scattered or degenerated. Whether oocyte was fertilized or unfertilized was more easily and quickly identified with the combination of Nomarski differential interference contrast microscopy and polarization microscope. The early and accurate identification of fertilization is beneficial for rescue unfertilized oocytes following conventional IVF.Tabled 1Clinical outcome following new rescue ICSIFertilization rates (%)Cleavage rates (%)Blastocyst rates (%)Pregnancy rates (%)Miscarriage rates (%)A(n=328)78.564.545.333.420.5B(n=87)52.462.333.225.525.6 Open table in a new tab
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