Morphological embryo assessment: Reevaluation

Objective: To assess whether the pronuclear score and embryo nuclear scoring have an additive value to day 2 morphology criteria in the prediction of the implantation rate (IR). Design: Retrospective clinical study. Setting: IVF Unit, Soroka University Medical Center. Patient(s): Analysis of all homogenous IVF fresh embryo transfers from 2008-2010. Intervention(s): Morphological evaluation of pronuclear scoring, embryo nuclear scoring, and day 2 embryo morphology scoring on embryos obtained from IVF or intracytoplasmic sperm injection (ICSI) cycles. Main Outcome Measure(s): Implantation rate of homogeneous transfers. Result(s): No statistical association was found between the pronuclear scoring system (Z) and IR. The pronuclear score Z3 had a significantly better performance than Z1, Z2, and Z4 (IR = 25.2%, 22%, 21.4%, and 11.8%, respectively). Assessment of the second day embryo morphology scoring (index [IDX]) was found to associate with IR. IDX1, IDX2, IDX3, IDX4, and IDX5 had an IR of 36.1%, 28%, 21.9%, 14.2%, and 0, respectively. The nuclear scoring including: 1 nucleus in all blastomeres, 1 nucleus in part of the blastomeres, no visualization, and multinucleation showed high association with IR = 32.7%, 22.9%, 14.8%, and 9.1%, respectively. The effect of the nuclear scoring on IR was lost in a multivariable analysis that included day 2 embryo morphology scoring. Conclusion(s): Our results suggest that there is no additive value in grading the zygote on day 1 or embryo nuclear scoring on day 2 to day 2 embryo morphology for the prediction of IR.