Glucose consumption of single post-compaction human embryos is predictive of embryo sex and live birth outcome

BACKGROUND: The aim of this study was to determine the relationship between nutrient utilization by the human embryo and its subsequent viability after transfer. METHODS: The embryos of 50 patients having single blastocyst transfer were cultured individually from Day 3 in 10 mu l drops of medium G2 under Ovoil in 5% O-2, 6% CO2, 89% N-2. Patient inclusion in the study was maternal age <= 38. Embryos were moved to fresh drops of medium every 24 h. Spent media samples, including controls containing no embryo, were coded, frozen and subsequently analysed blind. Analysis of glucose was performed by microfluorimetry. The sex of children born was recorded. RESULTS: Clinical pregnancy and live birth rates were 58 and 56%, respectively. Glucose consumption by embryos which resulted in a pregnancy was significantly higher on both Day 4 and Day 5 than that by embryos which failed to develop post-transfer (P < 0.01). Furthermore, on Day 4 female embryos consumed 28% more glucose compared with males (P < 0.05). Glucose uptake was independent of embryo grade. CONCLUSIONS: The rapid screening of glucose metabolism by the human embryo on Day 4 and 5 may prove to be a useful metric in the development of algorithms for the selection of embryos for transfer in human IVF. Also, the observed sex-related metabolic difference provides preliminary data to support the hypothesis that male and female human embryos differ in their physiology due to the presence of two active X chromosomes and an altered proteome for a finite time during the preimplantation period.