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

Does complete mechanical removal of the zona pellucida modify the outcome of transfer of vitrified–warmed human blastocysts? 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. 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). Total mechanical removal of the zona pellucida did not affect the tested parameters of clinical outcomes. [ABSTRACT FROM AUTHOR]