ICSI follows normal IVF procedures up to the point of egg collection
and sperm preparation. In ICSI, first the eggs are carefully separated
from the surrounding cumulus cells to check their suitability for injection.
Eggs must then be injected at the correct stage of maturity and therefore
it is usually not possible to inject all the eggs collected. The embryologist
will let you know how many eggs are suitable for injection. Those eggs
that are unsuitable for injection may then be mixed with the sperm as
in normal IVF procedures, but these eggs rarely fertilise.
The ICSI injection process involves holding a single egg by gentle suction
at one end of a microscopic tube and then picking up and injecting a single
sperm into the centre of this egg using an even finer glass pipette. The
eggs are then left overnight in the incubator for fertilisation to hopefully
proceed. The next day the embryologist assesses the eggs for fertilisation.
Two day after the egg collection and ICSI, the fertilised eggs (embryos)
are assessed again for signs of continued division and the best are selected
for transfer into the womb. To allow monitoring of this technique, all
the embryos replaced must be from either injected eggs (ICSI) or straightforward
IVF, the two cannot be mixed. Embryos not used can be frozen for later
use providing they are suitable (your embryologist will advise you at
the time of transfer).
Unfortunately, although ICSI can greatly improve chances of fertilisation
it can not be guaranteed. Although most patients will have embryos suitable
for transfer some couples may be unlucky and all the eggs may fail to
fertilise.
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