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 investiga te whether pyruvate uptake provides an improved criterion for selectin g embryos for transfer, we have measured uptakes by individual embryos noninvasively over 24-hr periods between the first day (day 1) postin semination and embryo transfer on day 2 or 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 f ailed to implant: 22.9 +/- 1.0 and 27.1 +/- 0.6 pmol/embryo/hr, respec tively on day 2, and 22.4 +/- 1.5 and 26.9 +/- 0.8 pmol/embryo/hr, res pectively, on day 3, but the wide range of uptakes by individual embry os was overlapping. Conclusion: We conclude that pyruvate uptake as th e sole criterion for embryo selection cannot predict which embryos wil l implant after transfer. Assessment of embryos using morphological an d developmental criteria, therefore, remains the most consistent, thou gh inefficient, indicator of pregnancy potential.