Pre-implantation genetic diagnosis and screening Pre-
implantation genetic diagnosis (PGD) is a very early form of
prenatal diagnosis that takes place during in vitro
fertilisation treatment (IVF). The embryos produced during the
IVF treatment are checked in the laboratory after fertilisation
to detect any abnormalities before they are implanted or
replaced in the uterus. Embryo biopsy and genetic examination
The technique used with PGD consists of two parts: an embryo
biopsy, followed by a genetic examination. An embryo biopsy is
carried out on all embryos (at the six to ten-cell stage) on day
three after fertilisation. To do this, an opening is first made
in the strong membrane surrounding the embryo (zona pellucida).
One or two cells are then carefully removed from the embryo.
These cells are examined in the genetic laboratory for possible
abnormalities in the structure or number of chormosomes. The
result of the genetic examination is known on day four or day
five after fertilisation. After the examination