Effects of reducing insemination time in human in vitro fertilization and embryo development by using sibling oocytes

Purpose: Recent studies showed a beneficial effect of reducing the time of sperm-oocyte interaction on fertilization division, and implantation rates of the oocytes obtained from randomized patients. In the present study, the effects of reduced insemination time on fertilization and embryo development were evaluated by using sibling oocytes from the same patient. Methods: A total of 464 oocytes from 36 patients was randomly allocated to be inseminated for either I hr (reduced) or 18 hr (regular). Results: Fertilization rates were not significantly different between reduced (135/229; 59%) and regular (150/235; 64%) groups. Cleavage rates and embryo quality were similar in both groups. A total of 135 embryos (73 from the reduced and 62 from the regular group) was transferred to 36 patients. Thirty-four embryos implanted in 18 patients (25.2% implantation and 50.0% pregnancy rates). Conclusions: Fertilization, cleavage, and embryo development from 1-hr insemination is comparable, not superior to those from an 18-hr insemination time, which is commonly used in in vitro fertilization programs. These data suggest that reduced insemination time can be used during in vitro fertilization to avoid unnecessarily longer exposure to spermatozoa.