The goal of embryo culture in an assisted reproductive (ART) program is to improve the quality of embryos developing in the laboratory and the chances of successful delivery of a healthy baby. Culture conditions for human embryos have evolved over the past thirty years.
Cleaving embryos normally develop in the fallopian tube, whereas the natural environment for morulla and blastocysts is the uterine cavity. Previously, it was conventional to use media permitting culture of human in-vitro fertilized embryos for 2 to 3 days to reach the four-to-eight cell stage, with additional embryo transfer to the patient. Premature replacement of the human embryo to the uterus may in part account for the low implantation rates associated with human IVF, with only approximately 10% of embryos transferred leading to a live birth.
Further basic research on the metabolism of invitro fertilized embryos revealed that there are specific needs, depending on the developmental stage of the preimplantation embryo. In addition, improvements in culture media resulted from an increased understanding of the environment of the oviduct and uterus. Since 1997, the extended culture in sequential serum-free culture media has attracted more attention. The ability to culture zygotes to the blastocyst stage should help to synchronize the embryo with the female reproductive tract, and to help to identify those embryos with little development potential.