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The advent of new culture techniques resulting in more than 60% of embryos developing in vitro to the blastocyst stage suggests that blastocyst transfer in humans with its potential to increase in-vitro fertilization success rates could be a feasible option. Blastocyst quality markers, however, are required to ensure that an increase in numbers is not achieved at the expense of lowering quality. We have previously reported a morphology based method for grading blastocysts. The current study sought to determine whether the secretion of pregnancy-specific beta-1-glycoprotein (SP1) (a trophoblast product known to be associated with fetal well-being) by blastocysts of differing quality was reflected in the morphological grading. SP1 concentrations were measured in the culture medium of grade 1 (n = 19), grade 2 (n = 4) and grade 3 (n = 4) blastocysts as well as vacuolated morulae (n = 6) daily from day 1 to day 14. Cumulative SP1 concentrations secreted by blastocysts were significantly higher than those secreted by vacuolated morulae. However, SP1 levels could not distinguish between blastocysts of differing morphological grades. The inconsistent pattern of secretion suggests that at this early stage of development, SP1 secretion is probably not sufficiently defined to allow any differences in levels to be reflected by the morphological grading.