Abstract: Purpose and Methods : The f requencies of micronucleus in polychromatic erythrocytes as well as the PCE/ NCE ratios in maternal bone marrow and in fetal liver induced by Cyclophsphamide (CP) and Ifosfamide ( IFO) were studied in pregnancy mice. Results : The result s suggested that the micronucleus f requencies in maternal bone marrow and in fetal liver did not change significantly compared to the cont rol group at the dose of 5mg/ kg. bw CP and IFO respectively. So were the PCE/ NCE ratios in both tissues. When the doses were raised to 15mg/ kg. bw , the micronucleus frequencies were 15. 40 ±3. 05 ‰and 12. 20 ±3. 56 ‰in maternal bone marrow , 23. 60 ±3. 65 ‰and 21. 00 ±5. 15 ‰in fetal liver for CP and IFO respectively , both were significantly different f rom cont rol group at P < 0. 05. When the doses were 30mg/ kg. bw , the micronucleus f requencies in both tissues increased more significantly , showing obvious dose - response relations. At the doses that inducing the increase of micronucleus f requencies of both drugs , the PCE/ NCE ratios declined dose - dependently in the two tissues. Both drugs showed greater genotoxicity respectively in fetal liver than in maternal bone marrow at the same dose. However , CP was more effective than IFO in the same tissue at the same dose. Conclusion : We concluded that CP and IFO could not only go into bone marrow but also go through placental barrier to induce chromosome damage. Thus protection for the workers producing or operating CP and IFO against the genotoxicity of the two drugs was necessary ; the clinical toxicity and side effect of both drugs to patient s should be inspected periodically.

Key words: cyclophosphamide, ifosfamide, bone marrow, fetal liver, micronucleus