Time-lapse videography reveals different morphokinetic profiles of human embryos displaying direct or reverse cleavage at different stages of development: A retrospective sibling embryo study

Objective: To investigate morphokinetic characteristics of embryos displaying either reverse cleavage or direct cleavage during the first, second or third cleavage cycle. Methods: A total of 167 in vitro fertilization and/or intracytoplasmic sperm injection treatment cycles undertaken by 167 women [aged (35.0±4.6) years] were included for reverse cleavage analysis, and a total of 167 in vitro fertilization and/or intracytoplasmic sperm injection treatment cycles undertaken by 167 women [aged (33.8 ±4.3) years] were included for direct cleavage analysis in this study. Using a sibling-embryo design, morphokinetic profiles (both before and after the onset of abnormal event) of embryos displaying reverse cleavage (n=241) or direct cleavage (n=244) were compared with their unaffected siblings (the controls) in the first, second and third cell cycles (n=32, n=142, n=562; n=195, n=412, n=205, respectively), at different developmental stages up to day 3. Results: Direct cleavage embryos demonstrated significantly delayed cleavage rates prior to the event regardless of developmental stage of the occurrence, while reverse cleavage embryos showed similar cleavage rates to their unaffected siblings. Post event, direct cleavage embryos sped up cleavage rates while reverse cleavage embryos slowed down. Conclusions: Altered morphokinetic profiles are displayed by direct cleavage embryos both before and after their occurrence and reverse cleavage embryos after the occurrence, which could potentially confound morphokinetic comparisons if not separated from their unaffected sibling embryos. Further study is warranted in order to fully understand the biological mechanisms of such events.