Predictive value of embryo grading for embryos with known outcomes

ObjectiveTo 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.DesignRetrospective analysis.SettingUniversity-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.