Mechanical zona pellucida removal of vitrified-warmed human blastocysts does not affect the clinical outcome

Abstract

Research question: Does complete mechanical removal of the zona pellucida modify the outcome of transfer of vitrified-warmed human blastocysts?

Design: In a prospective randomized controlled study, 419 couples were allocated to either zona pellucida-free (n = 209) or zona intact (n = 210) vitrified-warmed embryo transfer. Main outcome measures included clinical pregnancy, implantation and ongoing pregnancy rates.

Results: Transfer of zona pellucida-free blastocysts resulted in clinical pregnancy, implantation and ongoing pregnancy rates (35,9%, 33,9% and 32,1%, respectively), similar to those achieved with zona intact control embryos (39%, 36,4% and 33,1%, respectively).

Conclusion: Total mechanical removal of the zona pellucida did not affect the tested parameters of clinical outcomes.

Keywords: Assisted hatching; Blastocyst; Cryopreservation; Human; Total zona pellucida removal; Vitrification; zona pellucida.