Vitamin A acid (tretinoin, Retin-A) is a teratogen and the
documentation for this is quite compelling.  I believe however, that
this has been demonstrated only with *oral* tretinoin.  However, there
is no evidence that this is of any concern once the baby is fully
developed.  The question is how much appears in the milk and can this
quantity cause problems for the baby.  I do not think we have any
evidence about either of these issues.  However, we can make a guess.

Most skin applications result in very low blood levels of the active
ingredient.  This is likely the case for tretinoin.

I think there should be no concern.

Jack Newman, MD, FRCPC