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Unfrozen Oocytes Give Higher Success Rate for IVF

Fertilization, live birth rates higher for unfrozen compared with frozen oocytes

MONDAY, July 24 (HealthDay News) -- The use of unfrozen oocytes for in vitro fertilization (IVF) results in higher rates of fertilization and live births compared with frozen oocytes, according to a paper published in the July issue of Fertility and Sterility.

Kutluk Oktay, M.D., and colleagues from Weill Medical College of Cornell University in New York City performed a meta-analysis of reports on the success of IVF with intracytoplasmic sperm injection using oocytes slow-frozen between 1996 and 2004. This was compared with the success of IVF using unfrozen oocytes at their institution between 2002 and 2003.

The researchers found that using unfrozen oocytes resulted in significantly higher fertilization rates (odds ratio, 2.2), live births per injected oocyte (OR, 1.5), and implantation rates (OR, 4.66). The live birth rates per injected oocyte were 3.4 percent for frozen oocytes and 6.6 percent for unfrozen oocytes, while the live birth rates per attempt were 21.6 percent and 60.4 percent, respectively.

"In vitro fertilization success rates with slow-frozen oocytes are significantly lower when compared with the case of IVF with unfrozen oocytes," Oktay and colleagues conclude. Although oocyte cryopreservation with the slow-freezing method appears to be justified for preserving fertility when a medical indication exists, its value for elective applications remains to be determined.

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