Planar embryos have poor prognosis in terms of blastocyst formation and implantation

Normally, day-2 embryos show a crosswise arrangement of four cells with three blastomeres lying side by side. Cleavage anomalies include embryos that are characterized by a particular planar constellation of four blastomeres with presumed incomplete cleavage. Since little is known on the developmental fate of such conceptuses, within a 10-month period all consecutive patients were screened for day-2 planar embryos. A total of 64/2070 embryos with suboptimal blastomere configuration were detected (3.1%). In conventional IVF, planar embryos were significantly less frequent (0.7%) as compared with intracytoplasmic sperm injection (2.8%; P < 0.05) and cases of testicular sperm extraction (5.4%; P < 0.01). Interestingly, embryos with a cleavage anomaly showed better morphology both on day 2 (P < 0.005) and day 3 (P < 0.001). In contrast, blastocyst formation (P < 0.001) and blastocyst quality (P = NS) was higher in tetrahedral embryos. There was a significant increase in implantation rate if tetrahedral embryos could be transferred compared with when planar embryos had to be transferred (P < 0.01). It may be postulated that, in planar embryos, the mitotic spindle might have been affected, e. g. sperm centrosome composition or function, which in turn might have led to the observed cleavage anomaly. RBM Online (c) 2012, Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.