The impact of low oocyte maturity ratio on blastocyst euploidy rate: a matched retrospective cohort study

To investigate the association between a low oocyte maturity ratio from in vitro fertilization cycle and blastocyst euploidy.

A total of 563 preimplantation genetic testing (PGT) cycles (PGT cycles with chromosomal structural rearrangements were excluded) were performed between January 2021 and November 2022 at our center (average oocyte maturity rate: 86.4% ± 14.6%). Among them, 93 PGT cycles were classified into the low oocyte maturity rate group (group A, < mean - 1 standard deviation [SD]), and 186 PGT cycles were grouped into the average oocyte maturity rate group (group B, mean ± 1 SD). Group B was 2:1 matched with group A. Embryological, blastocyst ploidy, and clinical outcomes were compared between the two groups.

The oocyte maturity (metaphase II [MII oocytes]), MII oocyte rate, and two pronuclei (2PN) rates were significantly lower in group A than in group B (5.2 ± 3.0 vs. 8.9 ± 5.0, P = 0.000; 61.6% vs. 93.0%, P = 0.000; 78.7% vs. 84.8%, P = 0.002, respectively). In group A, 106 of 236 blastocysts (44.9%) that underwent PGT for aneuploidy were euploid, which was not significantly different from the rate in group B (336/729, 46.1%, P = 0.753). However, euploid blastocysts were obtained only in 55 cycles in group A (55/93, 59.1%), which was lower than the rate in group B (145/186, 78.0%, P = 0.001). The clinical pregnancy rate in group B (73.9%) was higher than that in group A (58.0%) (P = 0.040).

Our results suggest that a low oocyte maturity ratio is not associated with blastocyst euploidy but is associated with fewer cycles with euploid blastocysts for transfer, lower 2PN rates, and lower clinical pregnancy rates.