Noninvasive assessment of glucose and pyruvate uptake by human embryos after intracytoplasmic sperm injection and during the formation of pronuclei

Objective: To improve in vitro culture conditions and human embryo selection before transfer after IVF with intracytoplasmic sperm injection (ICSI). Design: A controlled, randomized, prospective study. Setting: University hospital–based IVF-ET program. Patient(s): Couples undergoing ICSI. Intervention(s): Culture of human embryos in the presence of 1 mM or 5.56 mM glucose and metabolic measurements with the use of noninvasive microfluorescence assays immediately after ICSI to the time of transfer. Main Outcome Measure(s): Embryo development, implantation rate, and glucose and pyruvate uptake. Result(s): Fertilization rates, early embryo development, and implantation rates were not significantly different between 1 mM and 5.56 mM glucose. Pyruvate uptake was significantly higher during the formation of the pronuclei, at 15 ± 0.7 and 11.4 ± 1.3 pmol/embryo/h for fertilized and unfertilized oocytes, respectively. Pyruvate uptake did not correlate with cleavage stage or embryo morphology. However, during the second day of incubation, pyruvate uptake was significantly higher for the untransferred embryos of pregnant women compared with nonpregnant women, at 17.9 ± 1.5 and 10.8 ± 1.0 pmol/embryo/h, respectively. Conclusion(s): The increased level of pyruvate uptake during fertilization reflects the increased demand for energy necessary for the formation of the pronuclei. However, the metabolic measurements could not improve the selection of embryos with the best implantation potential. Finally, the reduction of glucose concentration in the culture medium failed to improve embryo viability.