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The most common point of failure of assisted
conception treatments is after embryo transfer. It is
believed that one cause of this is the inability of
the transferred embryos to hatch, although why this is
the case is as yet unclear. It has been suggested that
current limitations of in vitro laboratory culture
causes changes to occur to the zona, which make it
more difficult for embryos to hatch. This does not
affect the best quality embryos, but those of more
borderline quality.
It is also thought that the cryopreservation
(freezing) of embryos causes changes to the zona,
which can reduce the incidence of hatching.
In order to counteract this, assisted hatching is now
being offered at a number of centres and aims to improve the chances of
successful hatching by the creation of a hole in the zona pellucida. There remain mixed views amongst the
medical and scientific community as to whether the
technique actually improves the chances of pregnancy,
but most agree that it is not detrimental and may be
potentially helpful in selected groups of patients.
There are several possible methods of carrying out
assisted hatching. The most widely practised being
whereby a fine glass pipette is used to blow weak
acidic medium on to the zona. This thins an area
before a hole is punched through the centre of the
thinned section. The procedure is carried out on day 3
of embryo development. By this time sufficient
cell-cell bonding has occurred to minimise the loss of
cells through the hole created.
A laser can also be made for making this whole and is
now more commonly used.
Who is it appropriate for
where the embryos selected for transfer appear
to have unusually thickened zonae
where the female partner’s age >40years
where failed implantation occurs after embryo
transfer of good quality embryos on two or more
occasions .
where the cycle involves the transfer of
frozen/thawed embryos.
Where there is elevated basal serum FSH (follicle
stimulating hormone) in the woman (10-12 iu/l)
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