【Objective】 To assess the effect of short time insemination (2 hours

2 h) on the polyspermy rate and the outcome of in vitro fertilization (IVF). 【Methods】 In this prospective study

658 patients were randomized divided into short time insemination group (group A) and standard insemination group (group B). The rates of fertility

polyspermy

usable embryos

clinical pregnancy and implantation were studied. 【outcome】 Sixty-one patients of the total participates were excluded because of no embryos available. The data of the other 597 patients were analyzed. There were 294 patients in the short co-incubation group and 303 patients in the standard insemination group. The fertility rate was significantly lower in group A than that in group B (68.8% vs 72.1%

P < 0.05). But the rates of polyspermy (11.4% vs 11.7%

P > 0.05)

usable embryos (86.5% vs 86.1%

P > 0.05)

clinical pregnancy (47.6% vs 42.6%

P > 0.05) and implantation (28.6% vs 26.5%

P > 0.05) had no significant differences. 【conclusion】 2 h insemination did not improve the polyspermy rate and the outcome of IVF.