Table II.
Nomenclature of morphokinetics parameters.
| Terminology | Description of the event | |
|---|---|---|
| tPB2 | The second polar body is completely detached from the oolemma | |
| tPNa | Appearance of individual pronuclei; tPN1a, tPN2a, tPN3a, … | |
| tPNf* | Time frame of pronuclei fading; tPN1f; tPN2f... | |
| tZ | Time of PN scoring (last time frame before tPNf) | |
| tn* | First time frame at which an embryo reaches n number of blastomeres (e.g. t2, t3, t4) | |
| tTM | Trichotomous mitosis at different stages | |
| tSC | First evidence of compaction | |
| tM | Time of completion of compaction process (in case some blastomeres are excluded, it might be difficult to assess the real time frame) | |
| tSB | Initiation of blastulation (first frame in which the blastocoel is visible) | |
| tB | Full blastocyst (last frame before zona starts to thin) | |
| tE or tEB | Initiation of expansion; first frame of zona thinning (also called TEyB ‘y’ corresponds to morphology of inner cell mass; ‘z’ corresponds to morphology of trophectoderm cells) |
|
| tHN | Herniation; end of expansion phase and initiation of hatching process (also called tHNyz) | |
| tHD or tHB* | Fully hatched blastocyst (also called tHDyz) | |
| Dynamic events and time intervals | Psyn | Syngamy, time from PN fading to the first cytokinesis |
| Not mentioned | Time between nuclear envelope breakdown and subsequent division to two cells | |
| s2 | Time between division to three cells and subsequent division to four cells | |
| s3 | Time between division to five cells and subsequent division to eight cells | |
| ECC1 | Duration of the first cell cycle (t2-tPB2) | |
| cc2 | Blastomere cell cycle: Duration of the second cell cycle (a = t3-t2, b = t4-t2) | |
| cc3 | Blastomere cell cycle: Duration of the third cell cycle (a = t5-t4, b = t6-t4, c = t7-t4, d = t8-t4) | |
| ECC2 | Embryo cell cycle: t4-t2 | |
| ECC3 | Embryo cell cycle: t8-t4 | |
| Blastocyst contraction | A decrease in blastocoel volume | |
| Cryopreserved/ warmed blastocyst | tRE | Time of the start of re-expansion (first frame in which the blastocoel reforms or increases in size) |
| tCRE | Time of completion of re-expansion (first frame the blastocyst occupies the whole perivitelline space) |
General comment: depending on the configuration of the TLT system, some events may not be seen. Table adapted from consensus paper (Ciray et al., 2014). Time zero (t0) may change from one study to another (mid-time for ICSI, standard IVF insemination, tPB2 or TPNf). These inconsistencies have to be taken into account when comparing data from different studies (Kaser and Racowsky, 2014).
*Parameters with the highest concordance between operators.