OBJECTIVE: This work was undertaken to evaluate the correlation between sperm cell morphology and fertilization after zona pellucida slitting in subfertile males. DESIGN: Twenty-two couples who failed at least one in vitro fertilization attempt because of lack of oocytes fertilization underwent a zona-slitting micromanipulative procedure. A total of 245 oocytes were retrieved and inseminated by three different modes: 151 oocytes underwent micromanipulation, 2 were damaged, and the remaining 149 inseminated by the husband's sperm (group A). Fifty-five oocytes were not manipulated and inseminated by the husband's sperm (group B), and 39 oocytes were not manipulated and inseminated by a donor sperm (group C). RESULTS: Fertilization rates were 26.8%, 5.5%, and 53.8% in groups A, B, and C, respectively, and differed significantly between group A and group B. The cleavage rates were lower for oocytes fertilized by the husband's sperm (48.6%) than that obtained by donor (90%), suggesting a sperm factor contributing to this phenomenon. The procedure was most efficient in patients with a total motile sperm count after preparation of greater than or equal to 5 million and with either normal sperm morphology or defects localized to the acrosome or tail region only. Sperm with nuclear morphological abnormalities demonstrated a marked reduction in fertilization potential. CONCLUSION: It is concluded that the zona-slitting technique enhances fertilization of severely subfertile sperm, and its efficacy is affected by sperm morphology and a threshold concentration of motile cells.
OBJECTIVE: This work was undertaken to evaluate the correlation between sperm cell morphology and fertilization after zona pellucida slitting in subfertile males. DESIGN: Twenty-two couples who failed at least one in vitro fertilization attempt because of lack of oocytes fertilization underwent a zona-slitting micromanipulative procedure. A total of 245 oocytes were retrieved and inseminated by three different modes: 151 oocytes underwent micromanipulation, 2 were damaged, and the remaining 149 inseminated by the husband's sperm (group A). Fifty-five oocytes were not manipulated and inseminated by the husband's sperm (group B), and 39 oocytes were not manipulated and inseminated by a donor sperm (group C). RESULTS: Fertilization rates were 26.8%, 5.5%, and 53.8% in groups A, B, and C, respectively, and differed significantly between group A and group B. The cleavage rates were lower for oocytes fertilized by the husband's sperm (48.6%) than that obtained by donor (90%), suggesting a sperm factor contributing to this phenomenon. The procedure was most efficient in patients with a total motile sperm count after preparation of greater than or equal to 5 million and with either normal sperm morphology or defects localized to the acrosome or tail region only. Sperm with nuclear morphological abnormalities demonstrated a marked reduction in fertilization potential. CONCLUSION: It is concluded that the zona-slitting technique enhances fertilization of severely subfertile sperm, and its efficacy is affected by sperm morphology and a threshold concentration of motile cells.