Growth retardation in human blastocysts increases the incidence of abnormal spindles and decreases implantation potential after vitrification.

Study Question: Does the human embryo growth rate affect the outcome of vitrified-warmed blastocyst transfer?

Summary Answer: Following vitrification, the incidence of abnormal spindle morphology was increased and the implantation competence was decreased in growth-retarded embryos compared with normally developing embryos.

What Is Known Already: Various types of spindle abnormality occur in human cleavage- and blastocyst-stage embryos. However, the incidence of abnormal spindle morphology in growth-retarded blastocysts is not known.

A closed system supports the developmental competence of human embryos after vitrification : Closed vitrification of human embryos.

Purpose: Closed-system vitrification may enable the risk of contamination to be minimised. We performed three studies to compare the developmental competence of human embryos vitrified using either a closed vitrification system (CVS; Rapid-i®) or an open vitrification system (OVS; Cryo-top®).

Methods: The first study was performed in vitro using 66 zygotes previously vitrified at pronuclear stage.