ABSTRACT
The formulation of new sequential culture media, capable of supporting the development
of viable human blastocysts, has reopened the discussion regarding the best day for
embryo transfer following in vitro fertilization (IVF). Although several laboratories
have reported overall increases in implantation rate and IVF efficiency following
the transfer of blastocysts, others have failed to observe any benefit from extended
culture. While culture conditions for the mammalian embryo undoubtedly have improved
significantly over the past few years, relatively little attention has been paid to
the quality of oocytes derived from ovarian hyperstimulation or the quality and receptivity
of the endometrium following such hormonal regimes. It appears that differences in
controlled ovarian hyperstimulation are among the major factors determining embryo
quality and subsequent implantation. This therefore has confounded comparisons between
different laboratories. In spite of this there are a growing number of reports demonstrating
that the advantages of extended culture and blastocyst transfer, such as increased
implantation rates, are not limited to specific groups of patients or specific etiologies.
Rather, blastocyst transfer may be of benefit to the majority if not all patients
attending for IVF.
KEYWORD
Amino acids - ART - carbohydrates - culture - embryo - IVF
