FERTILIZATION RATES USING INTRACYTOPLASMIC SPERM INJECTION ARE GREATER-THAN SUBZONAL INSEMINATION BUT ARE DEPENDENT ON PRIOR TREATMENT OF SPERM

Objective: To determine a suitable method of sperm preparation for use in micromanipulation. To compare the fertilization rates of sibling oocytes inseminated by intracytoplasmic sperm injection (ICSI) and subzonal insemination (SUZI). Design: Two methods of gamete micromanipulation to overcome male factor infertility were compared. Within this study, three trials were conducted to determine the most suitable method of sperm preparation. This method then was used to complete the study. Setting: Procedures were performed in a teaching hospital research environment. Patients: Ninety-six patients were recruited for this study, undergoing 99 stimulation cycles. Interventions: Sibling oocytes were inseminated by subzonal sperm or intracytoplasmic injection. Main Outcome Measures: Fertilization, zygote development, and pregnancy rates. Results: In the absence of manipulative pretreatment of sperm (trial 1), there was no difference in normal fertilization rates between ICSI and SUZI (19% and 25%, respectively). In the second trial there again was no sperm pretreatment for SUZI but, for ICSI, a polyvinylpyrrolidone (PVP) solution was used to reduce sperm velocity and the sperm tails were incised before injection. The fertilization rates were significantly different between ICSI (44%) and SUZI (17%). In the third trial, PVP was added to the sperm used for both types of insemination and the sperm tails also were incised for the ICSI insemination. Fertilization was again significantly different (16% for SUZI and 44% for ICSI). The trial 2 method of sperm preparation then was used to complete the study (trial 4) and confirmed the results of trial 2 (21% for SUZI and 42% for ICSI). The results suggest that ICSI can give improved fertilization compared with SUZI provided the sperm are treated before injection. No significant differences were found in the development rates of zygotes suitable for transfer or cryopreservation between the two micromanipulation methods.