At 3 months post-op hair transplant, will use of betamethasone lotion on the transplanted skin for 2 weeks affect the hair growt

It is best to ask your surgeon about post operative care as each doctor has their unique regimen. You must have a reason for why you want to use a certain medication and your doctor should be kept in on the loop. 

posh_hills_123,Thanks for the question.Why have you been prescribed a cortico-steroid cream?  We do not have the required information to be able to make a recommendation. It is necessary to take a detailed history, and closely examine your scalp.

Betamethasone is a steroid lotion that is used to decrease inflammation. Without knowing the reason you were prescribed or given the lotion, it’s difficult to assess your particular situation. In general, at 3 months post-op, this short course of usage should not negatively impact your growth; however, an underlying inflammatory skin condition may. Therefore, an in person clinical evaluation is recommended. 

You should check with your doctor to find out the answer to this question as it is would be inadvisable for me to give your such advice