Do hair clippers affect the growth of transplanted hair?

It is best to contact your doctor about post operative care and instructions since each doctor has a different regimen.  If your doctor said to avoid certain things, then you may want to follow your doctor's advice.  However, it is difficult to understand why you were told not to use clippers.  

ill_name_this_laterSorry, but there is no association with the use of clippers beyond the first two weeks after a hair transplant  and the subsequent growth of the transplant. It is recommended that proper care be employed to gently shampoo and style for the week following the transplant.All the best,Bernardino Arocha, MD

The use of hair clippers does not affect the growth of transplanted hair. However, the first 10 days, the transplanted grafts are very fragile. I recommend that you wait at least 2 weeks before you cut your hair to be sure that the grafts are healed. 

Grafts are very tenuous the first week after surgery and even minor trauma should be avoided.  Beyond that I cannot think of a reason not to trim hair.  That said, there may be something unique to you and/or the clippers you use that prompted your surgeon to give you that advice, so I would not advise you to ignore his/her suggestions. 

Clipping the frontal hair grafts should not be done for a month after a hair transplant for fear or the clipper pulling out a graft. After a month, it is ok

Use of hair clipper after 2 weeks of the procedure doesn't affect the hair growth. You can continue using clipper, their will not be any growth issue.