The effects of brief gamete co-incubation in human in vitro fertilization

Purpose: To investigate whether very short exposure of mature oocytes to sperm in vitro may affect the fertilization rates, embryo cleavage rates, and embryo quality between sibling oocytes in the same patient. Methods: Sibling oocytes of the same patient from 23 oocyte collection cycles were randomly allocated to the study group, with a 1-hr or 3-hr sperm-oocyte incubation, or the control group with the standard overnight gamete co-incubation. The fertilization rates, cleavage rates, and subsequent embryo quality were evaluated. Results: Our results showed no statistically significant differences in fertilization rates, embryo cleavage rates, and quality of the embryos between the study group and the control group. Conclusions: Since the present study showed that long exposure of the oocyte to sperm has no advantage over short exposure, we prefer shortening the oocyte-sperm incubation period for reducing the negative effect induced by nonphysiologically high concentrations of spermatozoa.