In couples presenting with mild infertility causes, intra-uterine insemination (IUI) is the first step in tackling the problem. Indications such as a sperm quality slightly lower than normal may be treated by this method.

IUI is a painless procedure, performed on the day of ovulation. The spouse / partner provides a semen sample which is subjected to appropriate laboratory processing. After processing, the isolated, motile sperm are concentrated into a very small volume (about 0.5 ml) and then placed in the uterus by means of a soft catheter. A prerequisite for performing IUI is that the Fallopian tubes of the female partner are "patent", i.e. allow passage of the motile spermatozoa, which can meet the egg and fertilize it.

An IUI may also be performed by using donor semen (heterologous insemination). In this case, the semen is provided by a sperm bank, either domestic, or from abroad.