Noneffectiveness of cryostorage duration on clinical and neonatal outcomes after single vitrified-warmed blastocyst transfers

In the current era of assisted reproductive technology, the strategy of single vitrified-warmed blastocyst transfer (SVBT) is acknowledged for positively impacting clinical outcomes and preventing the risk of multiple conceptions. Previous studies have indicated that blastocyst grade and the day of blastocyst positively correlate with outcomes. Moreover, storage duration has no significant effect on survival rates, clinical outcomes, and neonatal outcomes. However, some researchers express controversial opinions on cryostorage duration, and their findings suggest a negative impact on clinical outcomes. These results remain subject to controversy, and limited studies exist regarding the outcomes after SVBT. Therefore, our study aims to investigate the impact of the day of blastocyst, blastocyst grade, and blastocyst cryostorage duration on clinical and neonatal outcomes following SVBT in patients who underwent clomiphene-citrate-based minimal stimulation.

In this study, retrospective cohort study data collected from June 2015 to April 2023 included 2107 patients with first SVBT cycles who underwent a clomiphene-based minimal ovarian stimulation protocol or a drug-free natural protocol at the Ojinmed IVF Center. Patients were categorized into four groups based on blastocyst cryostorage duration: group 1 (< 2 months, n = 882), group 2 (3–6 months, n = 794), group 3 (7–12 months, n = 187), group 4 (13–24 months, n = 126), and group 5 (25–81 months, n = 118). The patient’s clinical and neonatal outcomes were compared with cryostorage duration after the propensity score matched.

Multivariable logistic regression analysis revealed that prolonged cryostorage duration insignificantly correlated with clinical outcomes. Additionally, neonatal outcomes are not correlated with cryostorage duration.

The patient must consider several parameters when selecting embryos for transfer, including the duration of cryostorage. Our study results show that for the first single vitrified-warmed blastocyst transfer of patients who underwent clomiphene citrate-based minimal stimulation, cryostorage duration does not affect outcomes.