RESUMEN

OBJECTIVE: 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. METHODS: 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. RESULTS: 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). CONCLUSION: 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.