Expansion and herniation: evaluation of the best pregnancy rate predictor after quarter laser assisted hatching in frozen blastocyst transfers.

Objective: To assess the recovery of thawed blastocysts submitted to quarter laser assisted hatching and examine potential correlations between the procedure and pregnancy rates.

Methods: This cross-sectional study included only single-blastocyst transfers performed from July 2017 to December 2018. A total of 765 blastocysts were thawed and immediately submitted to quarter laser assisted hatching in the zona pellucida; they were subsequently incubated for three hours until transfer time, at which time they were examined for collapse or expansion; expanded blastocysts were further evaluated for herniation.