| Intra-
cytoplasmic sperm injection (ICSI)
Intra- cytoplasmic sperm injection
(ICSI) is a technique for the treatment of extreme
male infertility in which sperm are injected directly
into the body (cytoplasm) of the egg. With ICSI we
might need no more sperm cells than we have egg cells.
The sperm we use frequently appear normal, but with
ICSI we can also make use of immature or poor-swimming
sperm.
When is ICSI Used ?
If there are even a small number
of sperm in the ejaculate, (or if sperm are affected
severely by antisperm antibodies during their maturation
process) sperm can be taken from a semen sample for
ICSI. If there are no sperm in the ejaculate, due
to an obstruction or to very low sperm production,
sperm can now be surgically retrieved directly from
the testes or the epididymis (TESE, PESA). Because
it is the genetic information carried in the head
of the sperm that needs to get into the egg, immature
sperm whose tails have not fully developed are adequate
for use in ICSI. ICSI is also sometimes used if there
is an apparent problem with fertilization in an IVF
cycle.
How is it done?
This procedure is very specialized,
and requires a great deal of skill on the part of
the scientist. All the procedures require the use
of special microscopes and micromanipulation equipment.
To put it in perspective, an egg is approximately
one-tenth of a millimetre across! The egg is gently
held with a suction pipette (on the left in the picture
below) while a sperm is picked up with a microinjection
needle, and deposited in the cytoplasm of the egg.
By doing this, several barriers to the sperm have
been removed, and fertilization usually follows. The
day after injection, we can tell whether fertilization
has taken place if there are two small spheres (pronuclei)
visible in the egg. If fertilization is successful,
the pre-embryo (zygote) is allowed to divide several
times in culture medium in the laboratory, before
it is transferred to the uterus or fallopian tube.
Any "spare" good embryos resulting from
the procedure can be frozen for more attempts later.
To summarize the ICSI process:
- The mature egg is held with a specialized holding
pipette.
- A very delicate, sharp and hollow needle is used
to immobilize and pick up a single sperm.
- This needle is then carefully inserted through
the zona (shell of egg) and in to the cytoplasm
of the egg.
- The sperm is injected in to the cytoplasm and
the needle carefully removed.
The eggs are checked the next morning for evidence
of normal fertilization
What is the success rate like?
ICSI has similar success rate to
IVF (about 32% of embryo transfer procedures produce
a clinical pregnancy). IVF has a slightly higher pregnancy
(about 36%), although this might be explained by the
problems inherent in some cases to the sperm generally
used in ICSI procedures. Frozen embryo transfers after
ICSI also have a similar success rate to those after
IVF (about 29%). These results do vary with female
age, with a substantial fall in pregnancy rates in
women over the age of 38.
What else should you know about ICSI?
Patients should realise that there
is a possibility that the same sperm problems the
father has could be inherited by his sons. Also, men
whose infertility is caused by a congenital blockage
of the epididymis or absence of the vas deferens might
carry one or more genes for cystic fibrosis. This
is a very serious disease affecting the lungs and
pancreas, and genetic screening of the prospective
parents is strongly recommended. The embryos can be
genetically screened before transfer by preimplantation
genetic diagnosis (PGD) or tests can be performed
during pregnancy (prenatal testing by amniocentesis
or chorionic villus sampling). There is also an extra
(thoug0h slight) chance that a child conceived with
ICSI could have a chromosome anomaly. This can also
be detected by PGD or pre-natal testing.
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