Perivitelline Space Abnormalities as Predictors of Fertilization and Embryo Quality in Intracytoplasmic Sperm Injection (ICSI) Cycles: A Prospective Observational Study.

BACKGROUND

Oocyte morphology is an important non-invasive indicator of developmental competence in assisted reproductive technology (ART). Among extra-cytoplasmic features, perivitelline space (PVS) abnormalities have shown inconsistent associations with fertilization and embryo quality after intracytoplasmic sperm injection (ICSI). This prospective observational study evaluated the association of PVS abnormalities with fertilization rates and embryo quality in ICSI cycles.

METHODOLOGY: Ninety-six ICSI cycles comprising 631 metaphase II (MII) oocytes were included. Oocytes were classified into four groups based on PVS morphology: normal PVS, large PVS (PVS-L), granular PVS (PVS-G), and combined PVS-L with PVS-G. Fertilization rates and day 3 embryo quality, graded according to the Istanbul Consensus criteria, were compared across groups using the chi-square test. Odds ratios (ORs) were calculated to assess the association with poor-quality embryos.

RESULTS

Fertilization rates were highest in normal PVS oocytes (147/172, 85.4%) and lowest in PVS-L oocytes (132/177, 74.5%), although differences were not statistically significant (p = 0.082). Embryo quality was significantly associated with PVS morphology. Grade I embryos were most frequent in the normal PVS group (88/147, 59.9%) and least frequent in the combined PVS-L + PVS-G group (15/89, 17.1%) (p < 0.001). Oocytes with combined PVS abnormalities had a markedly higher risk of producing poor-quality embryos (74/89, 83.1%) compared with normal PVS oocytes (59/147, 40.1%).

CONCLUSION

PVS abnormalities, particularly when multiple abnormalities coexist, are associated with significantly poorer embryo quality in ICSI cycles. Assessment of PVS morphology may provide a valuable non-invasive adjunct for evaluating oocyte competence, although clinical outcomes such as pregnancy and live birth were not assessed in this study.