Hi Rob,

Much of the breast's ductwork develops during the time between her puberty
till the first pregnancy. Each menstrual cycle grows the ducts a little
more. When she becomes pregnant, placental lactogen kicks in, the ducts
branch even more, and glandular tissue starts developing on the basement
membranes in the ducts.

If she has late onset of menstruation and only a few menstrual cycles before
pregnancy, it's theoretically possible that she'll develop less ductwork.
Less ductwork means less of a structure on which the glandular tissue will
develop, therefore less glandular tissue - therefore she'll need every cell
to work at full speed to make milk.

At least that's my understanding based on lots of reading and attending
lectures by dairy scientists like Floyd Schanbacher and Peter Hartmann. To
my knowledge, nobody has yet studied this thoroughly in women.

Linda J. Smith, BSE, FACCE, IBCLC
Bright Future Lactation Resource Centre
Dayton, OH USA
http://www.bflrc.com