Fertilization and embryo quality of mature oocytes with specific morphological abnormalities

Abstract

ObjectiveTo investigate fertilization and embryo quality of dysmorphic mature oocytes with specific morphological abnormalities obtained from intracytoplasmic sperm injection (ICSI).MethodsThe fertilization rate (FR) and embryo quality were compared among 58 dysmorphic and 42 normal form oocytes (control 1) obtained from 35 consecutive ICSI cycles, each of which yielded at least one dysmorphic mature oocyte, performed over a period of 5 years. The FR and embryo quality of 441 normal form oocytes from another 119 ICSI cycles that did not involve dysmorphic oocytes served as control 2. Dysmorphic oocytes were classified as having a dark cytoplasm, cytoplasmic granularity, cytoplasmic vacuoles, refractile bodies in the cytoplasm, smooth endoplasmic reticulum in the cytoplasm, an oval shape, an abnormal zona pellucida, a large perivitelline space, debris in the perivitelline space, or an abnormal polar body (PB).ResultsThe overall FR was significantly lower in dysmorphic oocytes than in normal form oocytes in both the control 1 and control 2 groups. However, embryo quality in the dysmorphic oocyte group and the normal form oocyte groups at day 3 was similar. The FR and embryo quality were similar in the oocyte groups with a single abnormality and multiple abnormalities. Specific abnormalities related with a higher percentage of top-quality embryos were dark cytoplasm (66.7%), abnormal PB (50%), and cytoplasmic vacuoles (25%).ConclusionThe fertilization potential of dysmorphic oocytes in our study was lower, but their subsequent embryonic development and embryo quality was relatively good. We were able to define several specific abnormalities related with good or poor embryo quality.

Evaluating the value of day 0 of an ICSI cycle on indicating laboratory outcome

“…The presence of a dark cytoplasm was associated with unfertilized oocytes, Z3 and Z4 scores. This is in accordance to literature as dark cytoplasm has been associated with lower fertilization rates 15 and embryos of poorer quality 47 . Granular ooplasm was associated with poorer prognosis Z-Scores, namely Z3 and Z4 moderate and poor cleavage stage embryo quality and were more likely to be discarded at any developmental stage.…”

“…Granularity of the ooplasm is correlated in literature with lower implantation potential and embryos of inferior quality 48 , 49 . Fertilization failure was not associated with ooplasm granularity in this study, an observation supported by part of published data 49 and contradicted by other studies 15 . The presence of vacuoles was associated with Z4 scores, supporting the observation that vacuoles have been correlated with a lower blastocyst formation rate 3 .…”

“…Certain oocyte features have been successfully associated with fertilization outcome, zygote formation, embryonic development and implantation potential 10 . Documented studied oocyte parameters include the cumulus oocyte complex (COC) 11 , the polar body 12 , the zona pellucida (ZP) 13 , the perivitelline space (PVS) 14 and the ooplasm 15 . In most cases the oocyte features were regarded as a dichotomous variable 15 and not a multifactorial or continuous as they present in reality.…”

“…Documented studied oocyte parameters include the cumulus oocyte complex (COC) 11 , the polar body 12 , the zona pellucida (ZP) 13 , the perivitelline space (PVS) 14 and the ooplasm 15 . In most cases the oocyte features were regarded as a dichotomous variable 15 and not a multifactorial or continuous as they present in reality. Hitherto, only a single systematic review has been performed on the predictive value of the oocyte characteristics reaching the conclusion that data were contradicting and further research was required 9 .…”

Ultrastructural and cytogenetic analyses of mature human oocyte dysmorphisms with respect to clinical outcomes

“…The large majority of studies on oocyte cytoplasmic dimorphisms provided individual embryological information, although the individual impact of these dimorphisms remains unclear as most of the clinical results are presented for pooled oocyte dimorphisms [33][34][35][36][37][38][39][40][41][42][43][44].…”