Wider implications of the findings: This study is the first analysing egg donors characteristics in several European countries.The study documents a considerable variation of donors' characteristics.These differences are probably mostly related to differences in national legislations, codes of practices, and culture.They may partly explain the differences in access and have a role on CBRC phenomenon.They have be considered to better understand the motivations for donation, which will presented in another abstract.
INTRODUCTION Blastocyst vitrication is now a routine procedure that allows patients to store high-quality embryos indenitely with a high expectation of pregnancy post-warming.1 Patients with multiple blastocysts will routinely transfer just a single fresh embryo (elective single-embryo transfer) to avoid multiple pregnancy,2 with the knowledge that their remaining embryos can be successfully frozen and stored until needed. At the time of warming, it will again be ideal to use just a single embryo from the freezer to maintain the eciency and safety of the process, particularly in younger patients, those who experienced a loss or miscarriage aer a previous transfer, or if the embryo is known to be euploid aer chromosome analysis.3 In attempting to use a single embryo and to give the patient the greatest possible chance of pregnancy, the embryologist is charged with recovering, warming, and culturing the embryo, and with accurately assessing the viability of the embryo before transfer. In addition, the embryologist needs to be aware of procedures that may limit or enhance the embryo's chance of implantation,4 such as timing of warming and transfer relative to uterine receptivity,5 culturing the embryo for an appropriate time before transfer, and assisted hatching (AH).6
Abstract Non‐invasive microanalytical methods have been devised to study the energy metabolism of single human preimplantation embryos. Psyruvate, which is added routinely to all media used to culture human embryos, is consumed throughout the preimplantation period, with glucose assuming an increasing role at embryo compaction and blastocyst formation. All of the glucose consumed may be accounted for by the appearance of lactate in the incubation medium. The enzyme hexokinase my be involved in regulating this aerobic glycolysis. There is cosiderable indirect evidence for the utilisation of endogenous as opposed to exogenous energy substrates, the most likely candidate being protein. Information on early human embryo metabolismis likely to find application in a number of areas: these include the improvement of techniques for assisted human conception, notably in the selection of embryos for transfer following In Vitro Fertilisation; the diagnosis of gentic defects at the preimplantation stage; increased undersding of the causes of implantation failure and miscarriage, and the development of novel post‐coital contraceptives.
