Influence of Oocyte Dysmorphisms on Blastocyst Formation and Quality

Objective: To identify the association between oocyte dysmorphisms and blastocyst developmental competence.

Design: Case-control study.

Setting: Private assisted reproduction center.

Patient(s): This study included 5,516 embryos, which were obtained from 605 patients undergoing intracytoplasmic sperm injection cycles in which ET was performed on day 5 of embryo development.

Intervention(s): Intracytoplasmic sperm injection and ET.

Main Outcome Measure(s): The morphologic characteristics of the blastocysts, namely the degree of blastocoel expansion and hatching status, the size and compactness of the inner cell mass (ICM), and the cohesiveness and number of trophectoderm cells, were correlated with oocyte dysmorphisms.

Result(s): Of the 5,516 embryos evaluated, 2,920 (52.9%) reached the blastocyst stage. The blastocysts' degree of expansion and hatching status were decreased by the presence of aggregates of smooth endoplasmic reticulum clusters, large perivitelline space, and shape abnormalities. The presence of a large perivitelline space also decreased the ICM and trophectoderm cell quality. Aggregates of smooth endoplasmic reticulum clusters also decreased the ICM quality, pregnancy rate, and the miscarriage rate.

Conclusion(s): The results presented here suggest that the individual identification of oocyte dymorphisms may be a prognostic tool for blastocyst development and quality. However, the results do not diminish the importance of cleavage-stage embryo morphology assessment to predict blastocyst development competence.