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University of Colorado Denver


Intracytoplasmic sperm injection (ICSI) is a laboratory procedure developed to help infertile couples undergoing in vitro fertilization (IVF) due to severe male factor infertility. ICSI involves the insertion of a single sperm directly into the cytoplasm of a mature egg (oocyte) using a microinjection pipette (glass needle). ICSI has largely replaced the two previously developed micromanipulation techniques, partial zona dissection (PZD) and subzonal insertion (SUZI), because it achieves higher overall fertilization rates.

A variety of sperm problems can account for male infertility. Sperm can be completely absent in the ejaculate (azoospermia) or present in low concentrations (oligospermia). They may have poor motility (asthenospermia) or an increased percentage of abnormal shapes and forms (teratospermia). There may also be abnormalities in the series of steps required for fertilization, such as sperm binding to and penetrating the egg. Deficiencies in any of these aspects of sperm function will generally lead to lack of fertilization.

ICSI can facilitate fertilization by sperm that will not bind to or penetrate an egg. It can also be used to treat men with extremely low numbers of sperm. However, ICSI is generally unsuccessful when used to treat fertilization failures that are primarily due to poor egg quality.


  • Very low numbers of motile sperm with normal appearance.
  • Problems with sperm binding to and penetrating the egg.
  • Antisperm antibodies (immune or protective proteins which attack and destroy sperm) of sufficient quality to prevent fertilization.
  • Prior or repeated fertilization failure with standard IVF culture and fertilization methods.
  • Frozen sperm collected prior to cancer treatment that may be limited in number and quality.
  • Absence of sperm secondary to blockage or abnormality of the ejaculatory ducts that allow sperm to move from the testes. In this situation, sperm are obtained from the epididymis by a procedure called microsurgical epididymal sperm aspiration (MESA) or from the testes by testicular sperm aspiration (TESA).

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 of 60% and cleavage rates of 80% or more are expected, but only 30% to 60% 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 outcome studies in Europe suggest that there is no evidence of increased incidence of major congenital malformations. Recent studies have demonstrated that the incidence of chromosomal disorders in couples seeking ICSI is considerable (5-10%). These disorders carried by the parents may be passed on to the child. For example, because some causes of male infertility related to genetic problems in the Y-chromosome, male offspring might have reproductive problems as an adult. Furthermore, approximately 1 in 20 individuals not using IVF/ICSI will have some birth defects and we expect a similar incidence in babies born as a result of the ICSI procedure.

University of Colorado Denver
Advanced Reproductive Medicine

Anschutz Medical Campus Office
Location: 1635 Aurora Court, Aurora, CO 80045
Mailing: PO Box 6510, Mail Stop F701, Aurora, CO 80045
Tel: 720.848.1690
Toll-free: 1.888.899.7441
Fax: 720.848.1678
Colorado Springs Office
4125 Briargate Parkway, Suite 350
Colorado Springs, CO 80920
Tel: 719.314.3333
Fax: 719.314.3344

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