Although the probability is very low, the take home message is that for clinical purposes, we should focus on the transfer of single spindle or a polar body, which would carry less mitochondria than the standard transfer of two
pronuclei after fertilization.
The timing of
pronuclei transfer (better early
after fertilization, about 8 hours
after insemination, referred to as «ePNT»), changes to the manipulation medium (removing calcium and magnesium, and reducing the amount of the protein that mediates the fusion event), and the use of a one - step medium in which the embryos remained for the duration of the manipulation, all were beneficial.