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New Method of Fertilization Could Improve IVF Success Rates

April 12, 2013

Intracytoplasmic sperm injection (ICSI) is a method of fertilization used in conjunction with in vitro fertilization (IVF) to address male factor infertility. The procedure involves selecting sperm after examination under 200-400 times magnification, then injecting one sperm into each egg. Only the sperm with normal appearance are selected.

A relatively new procedure, Intracytoplasmic Morphologically Selected Sperm Injection (IMSI) differs only in that sperm is examined under 6,300 times ultramagnification. IMSI is more costly than ICSI, but it could benefit fertility patients who have experienced failed IVF with ICSI cycles.

A study, published in the April issue of Fertility and Sterility, sought to compare both fertilization methods to determine which could provide better pregnancy outcomes. Data was examined from 9,413 cases presenting with male factor infertility and history of failed IVF cycles between 2006 and 2011. Patients were given the choice between IMSI and ICSI fertilization for their IVF cycles; 1,891 chose ICSI and 577 chose IMSI. Researchers discovered that pregnancy rates between the two fertilization methods were not statistically different, however delivery rates were slightly higher for IMSI patients than ICSI patients. Patients who experienced a failed ICSI cycle were then allowed to choose between ICSI and IMSI for their second cycle. Pregnancy rates were significantly higher (56%) for those who elected to use IMSI versus those who completed a subsequent cycle with ICSI (38%). Delivery rates were also higher for the IMSI group (28%) than the ICSI group (18%).

Results suggest an improved implantation rate and pregnancy rate with decreased miscarriage rates for couples utilizing the IMSI method of fertilization. IMSI presented nearly triple the chance of pregnancy and delivery for couples who experienced a failed ICSI cycle prior. However, couples who completed two cycles of IMSI had the lowest pregnancy and delivery rates, suggesting some level of chance or less stringent criteria for selecting sperm may prove beneficial to some couples.

Overall, ICSI seems to be a good first line treatment, with the more expensive procedure of IMSI being reserved for couples who fail one or more IVF with ICSI cycles.


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