Received July 13, 2019
Accepted December 14, 2019

Objectives: To evaluate the relation between morphology grading and morphokinetics parameters in blastocyst stage embryos cultured in a time-lapse system. Methods: This is a retrospective cohort study from our clinic database. Patients undergoing assisted reproduction treatment in autologous oocyte cycles between October 2017 and May 2019 using a time-lapse system were included in this study. Embryos were morphologically graded according to Gardner and Schoolcraft criteria and morphokinetic parameters were annotated. Results: Our results indicated that the time of pronucleous fading (tPNFf), cleavage to two-(t2), four-(t4), eight-cells (t8) and blastulation (tB) are significantly different according to the morfological quality of the blastocyst formed. Already in the early development stage, the tPNf, t2 and t4 differ good (AA, AB, BA, BB) from poor (CC) quality potential blastocysts. Time of cleavage to 8-cells sort embryos that will turn into AA morfology blastocyst from the ones with grade BB and ultimatly, earlier tB correlates with the best quality embryos (AA, AB, BA). Conclusion: Our results showed that the first kinetic parameters (tPNf, t2 and t4) may be used to distinguish top-graded from low-graded blastocysts. Between top-graded blastocysts, t8 was predictable to differ BB blastocysts from AA grading. And finally, tB can also be used to differentiate BB blastocyst from AA, AB and BA grading. These time-points parameters may be considered to be applied in a laboratory routine, even in centers without time-lapse machines.