External Quality Assurance Schemes for Reproductive Medicine

Definition of Morphokinetic Events

Morphokinetic event Definition
tPNappearance Time at which pronuclei formation can be first be identified
tPNfaded Time at which both pronuclei have faded
tn Time from insemination to completion of division to n cells
tSC Time from insemination to when the first cells of the embryo begin to compact
tM Time from insemination to formation of a morula, where all cells have compacted and cell membranes are unclear
tSB Time from insemination to start of blastulation, when the first sign of a cavity formation between two cells is visible
tB Time from insemination to formation of a full blastocyst; when the blastocoele cavity fills the embryo with less than 10% increase in its diameter
tEB Time from insemination to expanded blastocyst; when the blastocyst has increased in diameter by more than 30% and the zona pellucida has started to thin
THB Time from insemination to hatching blastocyst, when the trophectoderm herniation through the zona pellucida is first observed
Direct cleavage Direct or rapid (<5hours) cleavage from 1 to 3 or from 2 to 5 cells