Time from trophectoderm biopsy to vitrification affects the developmental competence of biopsied blastocysts

The present study aimed to examine the correlations of the time interval from trophectoderm (TE) biopsy to vitrification with the blastocyst survival rate and blastocyst outgrowth ability.

A total of 1,202 mouse blastocysts were randomly divided into control (non-biopsy) and TE biopsy groups. The biopsied blastocysts were vitrified at various time points. The survival rate after warming, blastocyst adhesion rate, and outgrowth area was investigated. Several biopsied blastocysts were cultured in a time-lapse incubator, and the time required for re-expansion was measured.

Blastocyst survival rates after warming and blastocyst adhesion rates were comparable between the control and biopsy groups. The area of trophoblast outgrowth in the 1-h biopsy group was significantly smaller than that in the control, 0-h biopsy, and 4-h biopsy groups (p = 0.0304, p = 0.0058, and p = 0.0029, respectively). Re-expansion of blastocysts was observed at a high incidence 1-2 h after TE biopsy.

The vitrification of biopsied blastocysts in the process of re-expansion impairs outgrowth competence; therefore, blastocyst vitrification should be performed immediately after TE biopsy and before initiation of re-expansion.