HUMAN PREIMPLANTATION EMBRYO SELECTION
DISCUSSION AND CONCLUSION
The ‘quality’ of an embryo is basically determined by
the gametes (quality of sperm, maternal age, etc.),
and the process of fertilization in vitro does not have
precise and specific culture media requirements.
However, it is clear that embryo culture after fertiliza-
tion does have more complex requirements. The idea
that the in vivo environment is better than in vitro
conditions does not always correspond to reality. To
evaluate new techniques and/or new culture media,
in vitro grown embryos must be transferred to the
uterus in order to avoid misleading observations based
upon morphology alone, which has been clearly
demonstrated to have its limitations. The significance
of specific animal models for human assisted repro-
ductive technologies (ART) is questionable. Although
the mouse model has been useful, due to significant
and specific differences in centrosome transmission,
speed of development, metabolic pathways, etc., it is
not a good model for human culture. Prior to and
during culture, it is important to be aware of, and
to control the interactions of different compounds
with each other and with the gas phase. In view of
the fact that some embryos arrest early in develop-
ment, embryo transfer at early stages is at times a
‘blind’ process. However, later transfer at the blasto-
cyst stage is also faced with the problem of ensuring
that the blastocysts are viable and healthy after their
period of extended in vitro culture.
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