Perivitelline space volume and embryonic outcomes in conventional IVF: a single-center retrospective study with...

To investigate the effect of oocyte perivitelline space volume on embryonic outcomes in conventional in vitro fertilization (IVF) cycles, and to provide an objective morphological quantitative index for evaluating oocyte quality.

A retrospective analysis was conducted on 950 metaphase Ⅱ (MⅡ) oocytes from 110 conventional IVF cycles in the Reproductive Medicine Center of Wenzhou People's Hospital from January to December 2022. PVSV was measured by an image analysis system, and the oocytes were divided into four quartile groups (Q1: <25%, Q2: 25%-50%, Q3: 50%-75%, Q4: >75%) due to the non-normal distribution of PVSV data. The fertilization rate, normal fertilization rate, day-3 (D3) high-quality embryo rate, blastocyst formation rate and high-quality blastocyst rate were compared among the four groups. Mixed-effects models were applied to adjust for confounding factors and intra-patient clustering effects, and to analyze the correlation between PVSV and embryonic outcomes.

PVSV presented a slight right-skewed non-normal distribution, and 90.91% of the cycles contained oocytes from two or more quartile groups. No significant differences were found in fertilization rate and normal fertilization rate among the four groups (P > 0.05). The D3 high-quality embryo rate increased progressively with the elevation of PVSV, while the blastocyst formation rate and high-quality blastocyst rate peaked in Q2 and Q3 groups and decreased significantly in Q1 and Q4 groups (P < 0.05). Mixed-effects models confirmed a significant inverted U-shaped nonlinear correlation between PVSV and the above embryonic developmental indicators, and PVSV was an independent predictor of the in vitro developmental potential of post-fertilization embryos, with the optimal PVSV values clustering around the 3rd-4th deciles (corresponding to Q2-Q3).

PVSV can serve as an objective and quantitative auxiliary indicator for laboratory-level oocyte quality evaluation in conventional IVF cycles, providing a reference for in vitro oocyte and embryo screening. This study only includes laboratory embryology outcomes and does not provide clinically meaningful outcomes such as implantation, clinical pregnancy, miscarriage, or live birth. Due to the limitations of single-center retrospective design and exclusive focus on in vitro laboratory outcomes, the clinical application value of PVSV, including its correlation with in vivo implantation, clinical pregnancy and live birth outcomes, needs to be further verified by multicenter prospective studies with comprehensive clinical follow-up data.