6-Mercaptopurine treatment of pregnant mice: effects on second and third generations.

The immunosuppressive drug 6-mercaptopurine is embryotoxic in mice. Of the surviving female offspring of mice treated with low doses of 6-mercaptopurine during pregnancy, despite normal body weight and general appearance, many were either sterile or, if they became pregnant, had smaller litters and more dead fetuses as compared to offspring of mothers that had not received the drug.