Intracytoplasmic sperm injection or ICSI,
used in conjunction with in vitro fertilization (IVF), has revolutionized the
treatment of severe male factor infertility. This procedure involves injection
of a single sperm through the outer shell (zona
pellucida) and the cell membrane of the egg and into the cytoplasm. ICSI may
be required when the male has very low numbers of motile (moving) and/or
abnormally shaped sperm, or where there are problems with the sperm penetrating
the egg. ICSI also can be effective when there are antisperm antibodies in the
semen, (products of the immune system which may otherwise attack and destroy
sperm before it can reach the egg), or when previous attempts at fertilization
with standard culture
systems and fertilization methods were not successful. Finally, ICSI may be
used when an infertility cycle relies on a limited number of sperm, including frozen
sperm collected prior to cancer treatment, or those obtained from the male’s
tissue using microsurgical
techniques. Semen
analysis and prior history will help us determine whether ICSI is likely to
be required as part of your infertility treatment.
The ICSI Procedure
During the ICSI procedure, an embryologist holds the egg in place with a thin
pipette (similar to a tiny, glass straw). An injection needle is used to pierce
the zona pellucida and inject the sperm. The embryologist then carefully
withdraws the needle, leaving the sperm in the cytoplasm of the egg. In less
than a minute, the zona closes naturally and the egg retains its normal shape.
ICSI provides substantial benefit in cases of severe male factor infertility;
however, there are some risks associated with it. The egg can be damaged during
the process and, in some cases, the zona is difficult to pierce. Although there
is no data to link ICSI to an increased risk of genetic abnormalities, some
evidence suggests that males with semen deficiencies have a higher frequency of
chromosomal abnormalities that could be passed on to their male children. As a
result, candidates for ICSI are carefully selected and, if necessary, undergo
genetic screening and counseling prior to IVF.
If ICSI is successful, it results in fertilization. Even so, the embryo may
still face problems related to fertilization in general – it may not divide or it may
stop growing at an early stage of development. If it develops normally, it may
be selected for transfer to the uterus.
