【Objective】To assess the outcome of slow-frozen/thawed embryo transfer (TET) between different culture time of the embryos frozen at day 3(D3) in vitro in natural and artificial cycles.【Methods】 A database was analyzed retrospectively concerning TET cycles covered 552 cycles

in which the number of thawed embryos ≥1 and ≤3 from February 2009 to December 2010. According to the different culture time after embryo thawing

they were divided into group A (ET at the thawing day) and group B (ET at the next day ofter embryo thawed). And these two groups were further divided into nature cycle and artificial cycle.【Results】Although there were not significantly different between the couples age

the number of embryos transferred and the embryos scale (P>0.05). The implantation rates of D3 frozen embryos in group B were significantly higher than those in group A in both of the nature cycles and the artificial cycles (17.9 vs 12.3

P<0.05; 17.3% vs 8.7%

P<0.05)

respectively. 【Conclusion】 The effect of extending incubation time of thawed embryos does not significantly effect the outcome of D2 freezing embryos. But in the TET cycles of D3 frozen embryos

ET at the next day of embryo thawed will be better for the embryo implantation.