Increasing the probability of selecting chromosomally normal embryos by time-lapse morphokinetics analysis.

OBJECTIVE: To study the differences in the cleavage time between chromosomally normal and abnormal embryos and to elaborate an algorithm to increase the probability of noninvasively selecting chromosomally normal embryos.

DESIGN: Retrospective cohort study.

SETTING: University-affiliated infertility center.

PATIENT(S): Preimplantation genetic screening patients (n = 125; n = 77 with ET), including cases of repeated implantation failure or recurrent miscarriage. A total of 504 embryos were analyzed.

INTERVENTION(S): Embryo culture within a time-lapse system.

MAIN OUTCOME MEASURE(S): Kinetic variables included the time to 2 (t2), 3 (t3), 4 (t4), and 5 (t5) cells as well as the length of the second (cc2 = t3 - t2) and third (cc3 = t5 - t3) cell cycle, the synchrony in the division from 2 to 4 cells (s2 = t4 - t3), and the interval t5 - t2. Implantation and clinical pregnancy rates were also analyzed.

RESULT(S): A logistic regression analysis identified t5 - t2 (odds ratio [OR] = 2.853; 95% confidence interval [CI], 1.763-4.616), followed by cc3 (OR = 2.095; 95% CI, 1.356-3.238) as the most relevant variables related to normal chromosomal content. On the basis of these results, an algorithm for embryo selection is proposed to classify embryos from A to D. Each category exhibited significant differences in the percentage of normal embryos (A, 35.9%; B, 26.4%; C, 12.1%; D, 9.8%).

CONCLUSION(S): Chromosomally normal and abnormal embryos have different kinetic behavior. On the basis of these differences, the proposed algorithm serves as a tool to classify embryos and to increase the probability of noninvasively selecting normal embryos.