BACKGROUND There are limited data on the impact of different gonadotrophin preparations on embryo quality. METHODS This evaluation was part of a randomized, assessor-blind, multinational trial, conducted in 731 women undergoing IVF after stimulation with highly purified human menopausal gonadotropin (HP-hMG; MENOPUR) (n = 363) or recombinant FSH (rFSH; GONAL-F) (n = 368). Ongoing pregnancy was the primary end-point [HP-hMG 27% and rFSH 22%; odds ratio (OR) (95% confidence interval, CI) 1.25 (0.89-1.75)]. All 7535 oocytes retrieved were evaluated daily until day 3 (embryo transfer) in a blinded manner both by local site embryologists and a central panel of three embryologists. RESULTS The proportion of top-quality embryos per oocyte retrieved was higher with HP-hMG (11.3%) compared with rFSH (9.0%) (P = 0.044) in the local assessment, but comparable in the central assessment (9.5 and 8.0%, respectively). Significant differences in favour of HP-hMG were observed for number of blastomeres and degree of fragmentation, while uniformity of blastomere sizes, localization of fragments, frequency of multinucleation and homogeneous cytoplasm were comparable between HP-hMG and rFSH. The live birth, ongoing pregnancy and ongoing implantation rates for top-quality embryos were higher with HP-hMG than rFSH [48 versus 32% (P = 0.038), 48 versus 32% (P = 0.038), 41 versus 27% (P = 0.032)]. Both the proportion of embryos with at least 50% surviving blastomeres after cryopreservation and embryos resuming mitosis were more frequent with HP-hMG compared with rFSH. CONCLUSIONS Composition of gonadotrophin preparations used during ovarian stimulation has an impact on some embryo quality parameters. The capacity to implant of the top-quality embryos derived from stimulation with HP-hMG appears to be improved, although the mechanism needs to be elucidated.