Impact of Inner Cell Mass Hatching Levels Before Vitrification on Clinical Pregnancy in Preimplantation Genetic Testing for Euploidy Cycles

ABSTRACT Purpose Does an association exist between the ICM/TE hatching levels of biopsied blastocysts before vitrification and implantation? Methods Total 541 single blastocyst transfers in PGT‐A cycles were collected. The degree of TE/ICM extrusion from the zona pellucida before vitrification was categorized as (1) ICM hatching level ≤ 50% and > 50%, (2) TE hatching level ≤ 25% and > 25%. Results TE hatching levels were not associated with clinical pregnancy probability ( p = 0.804). Multivariate regression analysis revealed a positive association between ICM hatching level ≤ 50% with implantation probability. Especially in the ICM Grade B group, blastocysts with ICM hatching level > 50% had a significantly lower clinical pregnancy rate (47.4%, 36/76) and ongoing pregnancy rate (39.5%, 30/76) than did blastocysts with ICM hatching levels of ≤ 50% (66.4%, 219/330 and 60.6%, 200/330, respectively) ( p < 0.01). Additionally, the proportion of apoptotic ICM cells was significantly higher in the ICM hatching level of > 50% group (90.0%, 9/10) than that in the ICM hatching level of ≤ 50% group (23.1%, 9/39) ( p < 0.001). Conclusion Blastocysts with an ICM hatching level of > 50% had the lower implantation potential, which may be related to the increased incidence of ICM cell apoptosis.