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.