I had a client once with nipples which invaginated.  Dr. Lawrence was in
town for a physician's conf. and I asked her to take a look at this woman.
She described her nipples as a congenital birth defect.  They  were
abnormally formed.  She did secrete milk and could pump, but there were no
nipples at all.  Just areolar tissue with slits, and down at the bottom of
the slit some malformed, polyp-like formations.  I would guess this is rare,
because I've seen it once in 20 yrs.  I see milder forms of inverting
nipples fairly often, and consider them a serious obstacle for initiating
lactation.  Mavis Gunther described the problem beautifully in the 50's in
her article, Instinct and the Nursing Couple (Lancet).

Barbara



Barbara Wilson-Clay, BSEd, IBCLC
Austin Lactation Associates, Austin, Texas
http://www.jump.net/~bwc/lactnews.html