IMSI (Intracytoplasmic Morphollogicaly-selected Sperm Injection) is used for a thorough morphological selection of the sperm that will fertilize the oocytes in an IVF cycle.

Once the sperm have been selected according to motility criteria, they are visualised under a particularly powerful microscope which allows the internal morphology to be analysed and the optimum ones to be selected for fertilisation.

IMSI could be an option after several unsuccessful IVF cycles and in some cases of severe teratozoospermia. It is not a technique that is generally recommended, as it entails disadvantages, such as the considerable duration of the procedure. In the specific cases where it has been proven to be effective, it is considered to increase implantation and childbearing rates at home and decrease abortion rates.