Intracytoplasmic sperm injection (ICSI) involves the injection of a
single sperm directly into an egg. This procedure improves the fertilization
rates when sperm cannot penetrate an egg. ICSI is most often recommended
for treatment of severe male factor infertility, due to very low sperm
counts, poor sperm motility, and/or increased numbers of abnormal sperm.
ICSI may also be recommended if fertilization did not occur in a prior
IVF cycle; however, ICSI is generally unsuccessful when used to treat
fertilization failures that are primarily due to poor egg quality.
ICSI is not a perfect technique. Some eggs will be damaged by the ICSI
process. Some eggs have plasma membranes that are difficult to pierce.
In other instances, the fertilized egg may fail to divide, or the embryo
may arrest at an early stage of development. Egg fertilization rates
are approximately 50% of mature eggs and 80% of fertilized eggs develop
into embryos. However, only 15 to 20 percent of egg retrievals produce
a baby in well-selected couples. Other factors such as poor egg quality
and maternal age may cause these percentages to drop.
Perinatal outcomes studies in Europe suggest that to date, there is
no evidence of increased incidence of birth defects in children conceived
using ICSI. However, there is no guarantee that all babies will be normal.
For example, because some causes of male infertility are unexplained
and/or related to genetic problems, male offspring might have reproductive
problems as an adult. Furthermore, approximately 1 in 20 individuals
in the general population will have some birth defect, and this risk
is likely to be similar in babies born as a result of the ICSI procedure.