Human metaphase II oocytes with narrow perivitelline space have poor fertilization, developmental, and pregnancy potentials

To analyze the fertilization, developmental, and pregnancy potentials in oocytes with narrow perivitelline space.

Perivitelline space (PVS) of oocytes was evaluated at the time of ICSI, and those without sufficient PVS were judged as oocytes with narrow PVS (NPVS oocytes), and those with sufficient PVS formation were judged as oocytes with non-narrow PVS (non-NPVS oocytes). The analysis included 634 NPVS oocytes from 278 cycles and 12,121 non-NPVS oocytes from 1698 cycles. The fertilization and developmental potentials of NPVS and non-NPVS oocytes were compared by calculating odds ratios using a mixed-effects logistic regression model. We also compared the embryo transfer outcomes of those used for single vitrified-warmed blastocyst transfer after developing into the blastocyst stage.

NPVS oocytes had higher odds ratios for degeneration (adjusted odds ratio [aOR], 1.555; 95% confidence interval [CI], 1.096–2.206; p = 0.0133) and 0PN (aOR, 1.387; 95% CI, 1.083–1.775; p = 0.0095), resulting in a lower 2PN rate (aOR, 0.761; 95% CI, 0.623–0.929; p = 0.0072). Even embryos with confirmed 2PN had lower odds ratios for cleavage (aOR, 0.501; 95% CI, 0.294–0.853; p = 0.0109) and blastocyst development (Gardner criteria; CC–AA) rates (aOR, 0.612; 95% CI, 0.476–0.788; p = 0.0001). Blastocysts developed from NPVS oocytes had significantly lower odds ratios for clinical pregnancy (aOR, 0.435; 95% CI, 0.222–0.854; p = 0.0156) than those developed from non-NPVS oocytes.

Oocytes with NPVS have low fertilization and developmental potential, as well as low likelihood of pregnancy.