Fertilization and early embryology: Comparison of pyruvate uptake by embryos derived from conception and non-conception natural cycles

The uptake of pyruvate by human embryos derived from naturalcycles in the first 24 h following fertilization was examined.Since only one egg was obtained and therefore only one embryotransferred to the woman, it was possible to relate pyruvateconsumption by a particular embryo to the outcome of that cycle(pregnancy or no pregnancy). The results showed that embryoshave a wide range of pyruvate uptake values (2–53 pmol/embryo/h)but that this variation was reduced significantly to an intermediaterange of values in those embryos that were able to implant (10–30pmol/embryo/h). An association was found between embryo morphologyand pyruvate consumption. Morphologically good embryos weremore likely to implant if they demonstrated an intermediatepyruvate uptake. However, poor embryos did not implant evenif they had a pyruvate uptake of 10–30 pmol/embryo/h.No relationship was found between the type of infertility andpyruvate consumption of individual embryos. It is suggestedthat the ability of an embryo to implant is multifactorial andthat both morphology and pyruvate uptake may be factors.