Comparing blastocyst recovery and blebbing following one-step warming under osmotic conditions with and without...

We investigated the optimal thawing solution for one-step warming and assessed the efficacy of the one-step warming method for blastocysts subjected to biopsy. Vit Kit-Warm NX Thawing Solution (TS; Irvine Scientific, Santa Ana, CA, USA; osmolarity: 1641 mOsm), Vit Kit-Warm NX Dilution Solution (DS; Irvine Scientific, Santa Ana, CA, USA; osmolarity: 896 mOsm), and Modified HTF Medium-HEPES (m-HTF; Irvine Scientific, Santa Ana, CA, USA; osmolarity: 280 mOsm) were used to perform one-step warming. Survival, recovery, blebbing rate, and recovery time were compared. In blastocysts that were not subjected to biopsy, the DS group showed a lower rate of blebbing than the TS and m-HTF groups (at least P < 0.05). The DS group also showed a shorter recovery time than the TS and m-HTF groups (P < 0.01). In blastocysts subjected to biopsy, the DS group showed a lower rate of blebbing than the m-HTF group (P = 0.0288). The DS group also showed a significantly shorter recovery time than the TS group (P = 0.0319). The results demonstrate that one-step warming achieved favorable post-warming outcomes under various osmotic conditions, regardless of biopsy status. The DS group exhibited the lowest blebbing rate and the shortest recovery time among the three osmolarity conditions evaluated. These findings suggest that, under our vitrification protocol, DS containing 0.5 M trehalose provided the most favorable post-warming morphological outcomes among the three solutions tested.