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Pre-implantation genetic diagnosis (PGD), conducted in conjunctiion with an IVF cycle, is a method to evaluate
the genetic makeup of a patient's embryos prior to selecting
those to transfer into the patient's uterus. PGD is performed
for patients who are usually not infertile, but have risk for
transmitting genetic diseases. More than 200 genetic disorders
are currently amenable to this procedure.
PGD is performed in association with in vitro fertilization
treatment (IVF) where multiple eggs are obtained, fertilized and resultant
embryos are cultured. PGD begins with the removal of 1-2 cells
from selected embryos on the third day of culture when each
embryo should contain between six and ten cells. The procedure
is called embryo biopsy and the extracted cell is subjected
to genetic tests. The embryos (now each lacking one cell) are
returned to culture and embryonic development continues. On
the fifth day, the results of the genetic testing are used to
select the most promising embryos for transfer at the blastocyst
stage of development [see blastocyst
culturing].
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