Predictive value of embryo grading for embryos with known outcomes.

OBJECTIVE: To compare pronuclear morphology (Z-score), day 3 embryo grade, and day 3 cell number in the prediction of successful implantation rates (IRs), including cycles in which all or none of the embryos implanted.
DESIGN: Retrospective analysis.
SETTING: University-based IVF center. PATIENT(S): Four hundred twenty-six fresh IVF day 3 transfers of 852 embryos in women <36 years of age from January 2000 to December 2003 in whom all or none of the embryos implanted. MAIN OUTCOME MEASURE(S): Evaluation of Z-scores, embryo morphology, cell number, and IR. RESULT(S): Day 3 parameters were more predictive than Z-scores. When early parameters were poor (Z-score) but late parameters were both good, the IR was 38%, compared with 4% when the Z-score was good but the late parameters were poor. CONCLUSION(S): Embryo grading systems are useful in the prediction of embryo implantation. In particular, cell number and embryo grade are more predictive than Z-scores. Therefore, late parameters have a better prognostic value than Z-scores when selecting embryos for transfer. Copyright 2010 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.