Confirmation of the beneficial effects of brief coincubation of gametes in human in vitro fertilization

Objective: To confirm whether brief exposure of human oocytes to spermatozoa in vitro results in equivalent fertilization rates and possibly better quality embryos than overnight coincubation and to determine if there was a difference in outcome with regard to the type of culture medium used. Design: Prospective distribution of gametes between treatments in sequential patients. Setting: Assisted reproductive technology program in private hospital, Patient(s): Consecutively treated subfertile couples entering an infertility program. Intervention(s): Assisted reproductive technology treatment for infertility involving oocyte retrieval and in vitro fertilization. Main Outcome Measure(s): When possible, the outcome of fertilization and embryo quality were compared when gametes were coincubated for 1 hour or overnight. Two different formulations of human tubal fluid were compared in some cases. Result(s): There was no statistically significant difference in fertilization rates between a brief or overnight coincubation of gametes or between the two treatment groups with regard to the type of culture medium used. The quality of the embryos was significantly better in the 1-hour exposure group. The embryos in Basal XI human tubal fluid medium were of significantly better morphological quality than their siblings in D3+ human tubal fluid medium. Conclusion(s): Coincubation of oocytes and spermatozoa for a shorter period produced embryos of superior morphological quality than the generally accepted overnight protocol. A simple glucose and phosphate-free human tubal fluid medium resulted in early cleavage embryos of better morphological quality than a medium supplemented with glucose, taurine, and glutathione. (C) 1998 by American Society for Reproductive Medicine.