From Herbs of Choice  by Varro Tyler, Pharmaceutical Products Press, there
is some good information.  None of the info (which I don't have time to
copy just now) indicates its use for pregnant women, and none of the
studies done would be sufficient for me, at least, to recommend it to BF
moms.  It may work for you mostly because of the intake of extra fluids.
  Send me your snail mail address and I could send you a copy of the info.
 Or look in your library for this book.  I trust this book because it is
not anecdotal, but uses studies from all over the world to weigh the pros
and cons.
Michelle Scott, RD,IBCLC in NH