IUI involves artificially introducing sperm into the woman's body rather than by sexual intercourse. The process is also called artificial insemination. It is simple and painless, but precise timing is needed to increase the chance of success. Both eggs and sperm have a limited life and must be brought together at the right time.
IUI is useful when:
some men do not produce enough strong, motile sperm to fertilize the woman in the usual way.
The neck of the womb (cervix) may sometimes form an impenetrable barrier to the man's sperm.
A couple may wish to start a pregnancy but be unable to do so for no obvious reason (unexplained infertility).
In these cases, the semen used is the husband's. Hence, is also called as AIH (Artificial Insemination with Husband's semen).
Some men do not produce any sperms at all (azoospermia). They can be treated with ICSI in some situations. However, if they can not afford this treatment, IUI using a sample from a semen bank can be performed.
In other situations, the male partner may have a genetic disorder which can be lethal if passed on to the child.
Here again, IUI is performed with a sample from a semen bank. Hence, it is called AID (Artificial Insemination with Donor's semen). The semen comes from an anonymous donor much like a blood donation. Also just like blood, it is put through a series of checks for infections and quality before being made available.
Mild stimulation of the woman's ovaries using hormones before artificial insemination improves the process of egg maturation and makes it easier to predict the time of ovulation.