Objective   To comprise the neural tube defects teratogenicity effects of cyclophosphamide and homocysteine.

  Methods   The pregnant rats were randomly divided into control and fourcy clophosphamide experimental groups and three homocysteine experimental groups on their bodyw eight.The cyclophosphamide intakes among four groups were 7.5, 10.5, 12.5, 15.0 mg/kg via intraperitoneal administration on the 13th day of gestation, and the homocysteine intakes among three groups were 600, 300, 150 mg/kg via mouth during pregnance.On the 14th day of gestation, three rats were randomly killed and embryos were checked through optical microscopy and transmission electron microscopy; The other rats were killed on the 20th day of gestation.

  Results   The group of 12.5 mg/kg had a high frequence of neural tube defects and a low frequence of death, the results from optical microscopy and transmission electron microscopy indicated some typical changes of apoptosis.But the positiveteratog enicity effects of homocysteine on rats were not be observed in homocysteine experimental groups.

  Conclusion   To make a model of neural tube defects, the intake of 12.5 mg/kg was feasible; neurons apoptosis might be involved in its teratogenesis, while rat was not sensitivity to homocysteine.