Autoimmune hepatitis and Imuran

My husband was diagnosed with autoimmune hepatitis a year ago. He's been put on medication and now he's taking 5 mg Prednisone and 100 mg Imuran a day.

My concern is that we won't be able to have children. I've read that Imuran is likely to cause damage to an unborn child if the mother takes it, but I haven't seen any definite test results on how the drug affects the male reproduction system.

Is it an unnessecary risk to try to conceive while my husband is taking Imuran, and if it is, is it a big risk to take him off Imuran for a period to let it dissapear out of his system? What alternative treatments could be used during this period?

Thanks!