Correlation between Cytoplamic Oocyte Maturation and Chromosomal Aneuploidies - Impact on fertilization, embryo quality and pregnancy.

Abstract

To establish the relationship between oocyte cytoplasmic maturation and its chromosomal status and determine the effect of this feature over the reproductive outcome in patients with sub-optimal fertilization in ART. Fifty couples who underwent ART were selected. From nineteen patients, 22 metaphase II-MII and 18 failed-fertilized oocytes after ICSI were studied. The first polar body was collected for chromosomal analysis by aCGH. Oocytes were processed by immunocytochemistry (ICC) to determine oocyte maturation: assessment of inactive MPF status and the conformation-alignment of the metaphase plate.Other 31 couples presented sub-optimal fertilization (<50%) after ICSI, and failed-fertilized oocytes were studied by ICC. Two groups were conformed according to the main feature observed: A) cytoplasmic immaturity and sperm premature chromosome condensation and B) sperm nuclear decondensation failure with mature cytoplasm. Regarding MII mature oocytes, 87% had a normal metaphase plate and 84% were chromosomally normal. Contrary, immature oocytes presented abnormal metaphase plate (86%) and just 33% were euploid. In failed-fertilized oocytes: 100% of mature oocytes had a normal metaphase plate and 71% were euploid. When oocytes were cytoplasmic immature, 37% of them were normal (metaphase plate) and 50% were chromosomally normal.The global rate of aneuploidies and metaphase plate disarrangements in immature oocytes (MII+failed-fertilized) were significantly higher than mature oocytes (P<0.05).In patients with sub-optimal fertilization, the percentage of top quality embryos and pregnancy rate was significantly higher in group B (P<0.05). Oocyte cytoplasmic immaturity is related to metaphase plate anomalies and aneuploidies. Fertilized oocytes, from a cohort with sub optimal fertilization with cytoplasmic immaturity, had poorer reproductive outcomes.