What
causes IVF to fail
During
an IVF treatment cycle, a number of problems may arise which cause the treatment
to be cancelled or to fail. These include the following:
- The ovaries may either
fail to respond to the stimulating drugs or over-respond. In the former
case the egg collection would not go ahead. In the latter case, it is Bridge
policy to continue with down regulation but we hold the estumulating injection
until it is safe to do the egg collection without risk of ovarian hyperstimulation.
- Very rarely, even
when ultrasound scans indicated the presence of follicles, no eggs will
be found during the egg collection procedure.
- The collected eggs
may fail to fertilise in the laboratory and therefore no embryos will be
available for transfer.
- The eggs may fail
to divide after fertilisation and therefore cannot be implanted into the
uterus.
- After the embryo
transfer, the embryos may fail to develop in the uterus. This is the most
common reason for an IVF treatment not to result in pregnancy.
Freezing
& storage of embryos
In cases where more than
three embryos result from an IVF treatment, it is sometimes possible to freeze
and store these embryos for five years in the first instance. This enables
women to have a further treatment without the need for ovarian stimulation
or egg collection.
In order
to prepare the uterus to receive embryos, a course of drugs is administered
to thicken the endometrium (the lining of the uterus). Embryos are then thawed
and replaced directly into the uterus. However, some embryos may deteriorate
during the thawing process and would therefore not be replaced. The pregnancy
rates for frozen embryo transfers (FETs) are generally lower than those using
fresh embryos.
Intra-cytoplasmic
Sperm Injection (ICSI)
The
microsurgical fertilisation technique of ICSI is currently the most advanced
technique available for the treatment of male infertility. It is used in
conjunction with IVF and involves an extremely precise microscopic surgical
procedure on an egg to assist fertilisation.
When
should ICSI be used?
ICSI can
be used in cases where the man produced only a very small number of sperm
which are incapable of penetrating the barriers surrounding the egg unassisted.
This is usually because the sperm have extremely poor movement or no movement
at all. ICSI is also mandatory when sperm is directly retrieved from the
testes.
What
does the treatment involve?
Eggs and
sperm are collected in the same way as in a normal IVF treatment. However,
unlike conventional IVF a single sperm is picked up from a prepared sperm
sample in a very fine glass needle and injected through the zona pellucida
and the egg membrane directly into the centre of the egg. In this way, the
sperm is not required to penetrate any of the surrounding barriers. The injected
eggs are then incubated for sixteen hours and checked to see if fertilization
has occurred. If fertilization does occur, up to three embryos are replaced
two days after the egg collection as in a normal IVF treatment.
Microepididymal
Sperm Aspiration (MESA) Percutaneous Epididymal Sperm Aspiration (PESA) &
Testicular Sperm Extraction (TESE/TESA)
Total azoospermia
(total absence of sperm in the ejaculate) can be due either to a blockage,
absence of the vas deferens or to a failure of the testes to produce spermatozoa.
The degree of this failure can be variable.
In the
first instance, it is quite easy to recover sperm directly from either the
testis itself or from the epididymis, which is like a small reservoir appended
to the testis. However, the sperm that is collected is not able to fertilise
the egg in the natural way and ICSI is always necessary. This leads to a
fertilisation rate of around 65%.
In cases
of testicular failure, it is now possible in around 50% of cases to collect
at least a few sperm by performing one or multiple testicular biopsies. Provided
some motile sperm are recovered, the chance of fertilization of the egg is
again extremely good.
In both
circumstances, it might be possible to freeze some sperm at the time of this
operation so that it can be uses during subsequent IVF/ICSI cycles, if the
first one was unsuccessful.
Sperm can
be recovered either by open surgery needle or aspivatio. During Microepididymal
Sperm Aspiration (MESA) - the scrotum is opened and under microscope sperm
is aspirated from the epididymis.
Percutaneous
Sperm Aspiration (PESA) is a less invasive technique whereby a small needle
is inserted through the skin directly into the epididymis to aspirate sperm.
Testicular
Biopsy involves taking one or several small samples of the testes - either
for analysis, or for the recovery of sperm in the most severe cases of azoospermia.
These operations are done as day cases under general or local anaesthesia
with or without intravenous sedation.
