Short coincubation of gametes in in vitro fertilization improves implantation and pregnancy rates: a prospective, randomized, controlled study

Objective: To examine the benefits of short coincubation of gametes compared to prolonged incubation in in vitro fertilization (IVF). Design: Prospective randomized controlled study. Setting: Hospital-based fertility center. Patient(s): One hundred thirty patients (group 1) and 129 patients (group 2). Intervention(s): Oocytes from group 1 were exposed to spermatozoa for 2 hours, and oocytes from group 2 were exposed to spermatozoa for 20 hours. Main Outcome Measure(s): Fertilization and cleavage rates, embryo quality, and pregnancy and implantation rates were evaluated. Estradiol (E-2) and progesterone (P-4) levels were measured in the wells of culture dishes after 2-hour exposure of oocytes/zygotes to spermatozoa in group 1 and after 20-hour exposure in both the groups. Result(s): There was no difference between the two groups in the fertilization rate and the number of embryos obtained. However, the proportion of grade 1 embryos was significantly higher among group 1 compared to group 2 patients. Clinical pregnancy and implantation rates were significantly higher among group 1 compared to group 2. The significantly higher levels of E-2 and P-4 in the 20-hour cultures compared with the 2-hour cultures may have been detrimental to embryo quality, pregnancy, and implantation rates. Conclusion(s): Coincubation of gametes for 2 hours with standard or high insemination concentrations of spermatozoa significantly improved embryo quality and the pregnancy and implantation rates compared with overnight incubation of gametes. ((C)2003 by American Society for Reproductive Medicine).