Intra-cytoplasmic sperm injection (ICSI) is a relatively new but well-established procedure first performed in 1992. The procedure was developed to help male factor infertility. The procedure involves injecting a single sperm into the cytoplasm of each egg using a fine glass needle. The first ICSI baby was reported in 1992. This procedure has all the stages of an In vitro Fertilization with the main difference of how the egg is fertilized.

This treatment is used on couples with severe male factor:

• Obstructive azoospermia, meaning obstruction in the sperm tubes that carry the semen from the testes to the outside, as happens with vasectomized men or men with congenital absence of these tubes.
• Oligospermia, has insufficient sperm to be able to produce conception. 
• Poor motility, which means sperm, may swim feebly or not at all.
• Abnormal shape, which means sperm may have problems penetrating the surface of the egg.
• The presence of sperm antibodies.
• Couples who have failed to achieve fertilization or had very poor fertilization following standard IVF treatment.
• When frozen sperm is limited in number and quality.
• Unexplained infertility.

Usually the sperm used for this procedure is collected by ejaculation; however, when this is not possible there are other ways to obtain the sperm, such as: Epididymal (testicular) Aspiration, TESA, MESA, or the open biopsy.
According with data published by the Society of Technology for Assisted Reproduction, the pregnancy rate after ICSI was 23.5%. In patients with less than 34 years of age there have been published pregnancies with ICSI per transfer of 49%. A rate of 14.8% has been achieved with an ICSI treatment a day after the failure of an oocyte fecundation with the conventional methods.