Selection criteria for human embryo transfer: a comparison of pyruvate uptake and morphology.

Purpose: Pyruvate uptake is higher in human embryos developing to the blastocyst stage than those arresting at cleavage stages. To investigate whether pyruvate uptake provides an improved criterion for selecting embryos for transfer, we have measured uptakes by individual embryos noninvasively over 24-hr periods between the first day (day 1) postinsemination and embryo transfer on day 2 to 3 and correlated the levels with implantation and pregnancy outcome.
Results: The mean uptake was significantly lower for embryos that implanted than for those which failed to implant: 22.9 +/- 1.0 and 27.1 +/- 0.6 pmol/embryo/hr, respectively on day 2, and 22.4 +/- 1.5 and 26.9 +/- 0.8 pmol/embryo/hr, respectively, on day 3, but the wide range of uptakes by individual embryos was overlapping.
Conclusion: We conclude that pyruvate uptake as the sole criterion for embryo selection cannot predict which embryos will implant after transfer. Assessment of embryos using morphological and developmental criteria, therefore, remains the most consistent, though inefficient, indicator of pregnancy potential.