Understanding IVF and ICSI: Two Key Fertilization Techniques
These two terms—IVF and ICSI—are frequently mentioned during visits to a fertility clinic. While both involve the same gametes (sperm and egg), they use different techniques to achieve fertilization.
What is ICSI?
ICSI stands for Intracytoplasmic Sperm Injection. In this technique, a single sperm is selected and injected directly into the cytoplasm of an egg using a fine needle. This is a highly precise method, often used when there are concerns about sperm quality or prior fertilization issues.
What is IVF?
IVF, or In Vitro Fertilization, involves placing a prepared sperm sample in a dish containing one or more eggs. Fertilization then occurs naturally, as one of the sperm penetrates the egg on its own.
Both IVF and ICSI are complex procedures that must be performed in a specialized embryology laboratory.
When Is ICSI Recommended?
Doctors may recommend ICSI under the following conditions:
- Poor sperm quality (abnormal count, motility, or morphology)
- Advanced maternal age (typically over 40)
- Previous failed IVF attempts
- Borderline sperm DNA fragmentation
When Is IVF Appropriate?
IVF may be suitable when:
- Sperm quality is normal (good count, motility, and morphology)
- The female partner is under 40
- Sperm DNA fragmentation is below 25%
Your fertility specialist will review your test results and determine which technique—IVF or ICSI—is most appropriate. In some cases, a split IVF/ICSI cycle may be recommended, especially in cases of borderline semen quality or unexplained infertility. Studies have shown that including ICSI for some of the eggs in such cases can help reduce the risk of total fertilization failure.
Importantly, research has found no significant difference in embryo quality between IVF and ICSI. One study concluded that «embryo quality does not seem to be influenced by the mode of fertilization (IVF or ICSI).” Moreover, live birth rates are more strongly correlated with embryo quality than the fertilization method used.
Some fertility centers prefer to use ICSI in all cases due to its slightly higher fertilization rates, but this approach is still debated among specialists.
Final Thoughts
The decision to use conventional IVF or ICSI should be based on a thorough evaluation of each couple’s specific fertility profile. Your specialist will guide you through this decision, considering the true fertilization potential of the gametes and the most effective strategy for your case.
References:
Conventional in vitro fertilization versus intracytoplasmic sperm injection in patients with borderline semen: a randomized study using sibling oocytes. Van Der Westerlaken, Naaktgenoren N. Fertil Steril. 2006 Feb;85(2):395-400.
Fertilization of IVF/ICSI using sibling oocytes from couples with subfertile male or unexplained infertility. Li Z, Lin H, Xiao W. J Juazhong Univ Sci Technolog Med Sci. 2004;24(4):365-8,384.
Comparison of embryo quality between intracytoplasmic sperm injection and in vitro fertilization in sibling oocytes. R.Yoeli, R. Ovieto, J. Ashkenazi. J Assisted Reprod Genet. 2008 Jan;25(1):23-28.
Pregnancy outcome and live birth after IVF and ICSI according to embryo quality. Patricia Fauque, Roger Leandri, Francoise Merlet. J Assisted Reprod Gent. 2007 May;24(5):159-165.