Intracytoplasmic Sperm Injection (ICSI)

ICSI at a glance

  • Intracytoplasmic sperm injection (ICSI) is the procedure during which an embryologist injects a single sperm directly into the woman’s egg as part of the in vitro fertilization (IVF) procedure to aid in fertilization.
  • ICSI is used for male infertility conditions or when previous IVF attempts have failed.
  • At University of Colorado Advance Reproductive Medicine (CU ARM) our ICSI fertilization rate per egg injected is above 80 percent.
  • Birth defects in a child born after an ICSI procedure that results in pregnancy are rare.

About ICSI

Intracytoplasmic sperm injection (ICSI) is an assisted reproduction procedure to aid egg fertilization. During normal egg fertilization, a sperm attaches to the egg’s outer protective layer called the zona pellucida, which is the equivalent of the eggshell in bird eggs. The sperm then has to penetrate the zona and enter the inside of the egg, called the cytoplasm, which is where fertilization occurs. If sperm quality is poor, or if the egg zona is impenetrable, we may use ICSI, which injects a single sperm directly into the egg.

ICSI is used in conjunction with IVF. For traditional IVF, 50,000 or more sperm are mixed with an egg in a small dish at a laboratory to achieve fertilization. ICSI, however, employs a tiny needle to inject the sperm into the egg’s center. Once this is complete, the IVF process continues as normal: the fertilized egg(s) grow in the lab for two to five days to develop as an embryo(s), then are transferred to the woman’s uterus to implant, grow and hopefully develop into a full-term pregnancy.

Video: ICSI in action

Indications for ICSI

ICSI is used for female and male infertility conditions, such as:

  • Low sperm production.
  • Irregular sperm shape or movement.
  • Few eggs retrieved during IVF.
  • Sperm that have trouble attaching to the egg.
  • Eggs with a thick zona pellucida.
  • Unexplained infertility.
  • Blocked male reproductive tract that keeps sperm from releasing.

Occasionally, even with normal sperm parameters, the fertility doctor may recommend ICSI due to previous fertilization failure or when the sperm is used to inject previously frozen eggs.

How is ICSI performed

The procedure is generally performed on as many eggs as possible. The lab embryologist views the sperm and eggs through a high-powered microscope.

  • A mature egg is held in place with a specialized instrument.
  • A very sharp, hollow glass needle, known as a micropipette, is used to draw in a single sperm.
  • The needle is then carefully inserted into the cytoplasm and injects the sperm.
  • The needle is carefully removed in order to not damage the egg.
  • The process is repeated for all eggs that are to be fertilized.
  • The embryos (fertilized eggs) are grown in a lab for three to five days.

Any remaining embryos from the procedure can be frozen for future use. The direct risk from ICSI is that the procedure may damage some of the eggs injected with sperm.

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ICSI success rates

ICSI fertilizes 50-80 percent of eggs, according to the American Society for Reproductive Medicine. Lower results may occur if ICSI damages the egg, injected sperm does not result in fertilization, or the fertilized embryo stops growing. At CU ARM, our ICSI fertilization rate is consistently above 80 percent.

Once fertilization does occur, the chance of giving birth to a single baby, twins or triplets is the same as with traditional IVF.

How ICSI affects a baby’s development

According to ASRM, a woman conceiving naturally has a 1.5 percent to 3 percent chance that the baby will have a major birth defect. Children born after an IFV pregnancy are at a slightly higher risk for birth defects and using ICSI does not increase that risk.

Conditions that have been associated with the use of ICSI include Beckwith-Wiedemann syndrome, Angelman syndrome, hypospadias and sex chromosome abnormalities. Some infertility problems in ICSI-conceived children may be genetic. For example, if the man whose sperm was used had infertility issues, boys conceived with the use of ICSI may also have infertility issues as adults.