['To assess the combined effect of endometrial thickness and cumulative embryo score (CES) on pregnancy rates in assisted reproduction cycles compared to the effect of each of these factors considered individually.', 'Retrospective review of 2001 IVF pregnancy outcomes with respect to endometrial thickness and CES.', 'One hundred fifty-five IVF cycles were reviewed. Endometrial thickness ranged from 6.4 to 22 mm. CES ranged from 16 to 194. CES scores above 50 correlated with improved pregnancy rates (31%) over those less than 50 (12.5%). CES scores above 150 were correlated with a further doubling in pregnancy rates (66%). Endometrial thickness alone or in combination with cumulative embryo score did not improve the prediction of pregnancy.'] Is cumulative embryo score , not endometrial thickness , best for pregnancy prediction in IVF?