ABSTRACT
<p><b>OBJECTIVE</b>To analyze the possible causes of total fertilization failure (TFF) in conventional in vitro fertilization (IVF).</p><p><b>METHODS</b>We included in this study 552 couples who accomplished the first conventional IVF cycle in our center from January 2007 to August 2008. All the males met the Kruger/Tygerberg criteria, with the teratozoospermia rate < 96% in the previous 12 months and the postwash motile sperm > 1 million on the day of egg retrieval. The eggs were fertilized totally by conventional IVF.</p><p><b>RESULTS</b>Of the total number, 515 couples got zygotes by conventional IVF, with a fertilization rate of 78.67%, and 37 suffered TFF. The rates of primary infertility and teratozoospermia were significantly higher in the TFF group than in the fertilized group (P < 0.05). There were no statistically significant differences between the two groups in the number of controlled ovarian hyperstimulation (COH) days, the number of oocytes retrieved, the dose of gonadotropin (Gn) used, the age of the couples, the length of protocols and the rate of oligoasthenozoospermia.</p><p><b>CONCLUSION</b>Intracytoplasmic sperm injection (ICSI) can be considered for at least some of the oocytes to avoid unnecessary fertilization failure in teratozoospermia patients by Kruger/Tygerberg strict criteria.</p>