The Effect Of Metaphase Ⅱ Human Oocyte Morphology On The Development Of Embryo And The Rate Of Blastocyst Formation In Intracytoplasmic Sperm Injection Cycles

OBJECTIVE:To evaluate the contributing factors of metaphase Ⅱ (MⅡ) human oocytemorphology in intracytoplasmic sperm injection (ICSI) cycles and the influence ofspecific oocyte morphologic features (morphotypes) on embryo quality and the rateof blastocyst formation after ICSI. Providing the laboratory an effective predictor ofhow to select oocytes before in vitro fertilization (IVF)，the identification of oocytequality markers when a low number of oocytes can be used for IVF，and how toimprove the quality of oocytes in the clinical. Ultimately come to the purpose ofimproving embryo quality and clinical outcomesMETHOD(S)：Choose all the patients who need do ICSI from May2011to February2012inour reproductive center. Fifty four consecutive ICSI cycles. Only couples affected bysevere male factor infertility were excluded. Using conventional superovulation longprogram. A total of812metaphase Ⅱ (MⅡ) oocytes were selected from the cohort ofoocytes obtained from each patient and evaluated for morphologic appearance. Theoocytes retrieved in these cycles were divided into (A) normal oocytes；(B) oocyteswith extracytoplasmic abnormalities(fragmented first polar body、abnormal firstpolar body，dark zona pellucida，large perivitelline space and oocytes with shapeabnormalities)；(C) oocytes with cytoplasmic abnormalities(dark cytoplasm，granular cytoplasm， refractile body and intracytoplasmic vacuoles). ICSI wasperformed following conventional techniques. ICSI was performed only on oocytesin metaphase Ⅱ. Immature or very poor oocytes were not injected. Cleaving embryoswere evaluated on day2or day3and blastocyst formation on day5or day6afterICSI. In this study，we compared the fertilization rate，cleavage rate，embryo qualityand the rate of blastocyst formation after ICSI as they relate to oocyte morphology.Resulting assessment if metaphase Ⅱ human oocyte morphology significantly impacton embryo quality and the rate of blastocyst formationRESULT(S)： (1) In the group (A) with normal oocytes，the fertilization rate and cleavage ratewere62.9%and87.3%，higher than which were60.3%and86.1%in the group (B)，57.4%and83.4%in the group (C)，but statistics compare no significant differences(P＞0.05). The incidence of excellent and good quality embryos and the rate ofblastocyst formation were statistically significantly higher in the group (A) ascompared with those of the group (B)(25%vs11.33%，P＜0.05)and the group (C).(2) There was a presence of abnormal I polar body，large perivitelline space andvacuoles related to a lower fertilization rate (71.2%,79.1%and70.3%). Cytoplasmicdysmorphisms of the oocyte, including accumulation of smooth endoplasmicreticulum, were associated with poor developmental performance. No impact of theother MⅡ oocyte features on fertilization rate was observed.(3) Pronuclear morphology was effected by the presence of a large perivitellinespace, diffused cytoplasmic granularity, and/or centrally located granular area. Noimpact of the other MⅡ oocyte features on pronuclear morphology was observed.(4) Oocytes with poor morphology (many vacuoles，granularity or fragments incytoplasm)especially centrally located granular area led to poor-quality embryos.The incidence of excellent and good quality embryos was significantly lower (OR2.26，95%CI1.25–4.08) compared with oocytes displaying all the othermorphologic features.(5) Differential weighting of these characteristics was included in a new embryoscoring system, which showed a strong correlation with the rate of blastocystformation. According to the odds ratios obtained for each oocyte morphotype toreach at least one outcome, an MⅡ oocyte morphologic score (MOMS) wascalculated. A significant relationship was found between MOMS and female age，female basal FSH，and clinical outcome.CONCLUSION(S):(1) The outcome of ICSI is related to the quality of the oocytes retrieved.(2) Morphologic evaluation before ICSI helps to identify MⅡ oocytes withhigher developmental potential.(3) Weighting individual morphological characteristics of zygotes and embryos and combining them into a cumulative embryo score can improve selection ofembryos for transfer.(4) Because sample size is small，whether morphological characteristics of MⅡoocytes significantly impact on the rate of implantation and pregnancy is not sure.