Intracytoplasmic sperm injection (ICSI)
Intracytoplasmic sperm injection (ICSI) at a glance
- ICSI is a laboratory procedure that aids in fertilization during in vitro fertilization (IVF) by injecting a single sperm directly into the cytoplasm of a woman’s egg that has been retrieved from her ovary.
- ICSI is used for male infertility conditions due to poor sperm quantity, quality or movement, for women whose eggs’ outer shells are too thick, or when previous IVF attempts have failed.
- According to the American Society for Reproductive Medicine (ASRM), 50 to 80 percent of eggs injected with sperm will successfully fertilize.
What is ICSI?
Intracytoplasmic sperm injection (ICSI) is an assisted reproductive technology that may be used in conjunction with IVF. While similar to standard IVF in which a doctor collects eggs and sperm from each partner, the difference is in how fertilization is achieved.
In conventional IVF, the egg and a large number of sperm (about 50,000) are mixed together in a laboratory dish. For many couples, the quantity and quality of sperm required for this process to work is hard to achieve. In these cases, conventional IVF is not a viable option. ICSI however, increases the likelihood of IVF success.
During IVF with ICSI, a man’s semen is prepared by separating the live sperm from dead sperm and other debris in the semen. A laboratory embryologist then uses high-powered magnification to guide a small needle that injects a single, viable sperm through the outer shell (zona pellucida) and into a retrieved egg’s cytoplasm. If fertilization is successful, embryos will develop that can be transferred into the woman’s uterus or frozen for use in a future IVF treatment.
Since very few sperm are required and the ability of the sperm to penetrate the egg is no longer an issue, couples using ICSI have a greater chance of achieving pregnancy than with just IVF alone.
Who should consider ICSI?
ICSI is particularly effective for male factor infertility conditions including:
- Low quantity of sperm production, inadequate for conventional IVF or intrauterine insemination (IUI).
- Variable factors of sperm quality, including trouble attaching to the egg.
- Blockages in male reproductive tracts that keep sperm from releasing.
- Poor motility (movement), making it difficult for the sperm to move through a woman’s reproductive tract.
In some cases, the outer layer of the woman’s eggs is too thick or hard for a sperm to be able to penetrate it under normal circumstances, a problem that ICSI bypasses. When previous attempts at IVF are unsuccessful, some patients may opt to try ICSI, even if the man’s sperm quality is normal.
Success rates of ICSI
Between 50 to 80 percent of inseminated eggs are successfully fertilized using ICSI. Pregnancy success rates for embryos created using ICSI are the same as with traditional IVF, according to ASRM.
While fertilization rates using ICSI are high, not all fertilized eggs develop into healthy embryos. Factors such as a woman’s age, egg quality and fertilization issues may result in an abnormal embryo.
Risks of ICSI
ICSI is a form of assisted reproductive technology that has been used since the early 1990s. Some research has linked ICSI to a slightly increased risk of:
- Conceiving a baby with sex chromosome abnormalities or certain genetic defects.
- Passing on low sperm count to a male child.
These risks are not conclusive, and some may be caused by underlying infertility rather than ICSI itself. Men with very low sperm counts have a higher risk of passing on genetic defects overall, and may be encouraged to pursue preimplantation genetic testing prior to ICSI.
Another risk of ICSI is also a risk of IVF itself – increased chance of multiple births versus natural conception. Multiple births (twins or more) carry a higher risk of complications to both the mother and the babies. This risk can be minimized by carefully controlling the number of embryos transferred to a woman’s uterus. ASRM reports that once fertilization via ICSI occurs, the chance of a multiple pregnancy is the same as for IVF without ICSI.