I'm looking for some published research into the effects of medicine given
during labor and reduced milk production.

I read a passing mention that the endorphins to counteract the
catecholamines experienced during labor promote the hormone prolactin. Since
the pituitary is involved in secreting the endorphins as well as the
prolactin, any artificial "narcotic" would stop/reduce the natural
endorphins and subsequently the prolactin, right?. I've read of research
that shows "drugged" babies and mothers have many more problems nursing, but
I haven't heard of any specific links to a  reduced prolactin level.

Thanks,
--Kelly Harrison
  Nursing Mothers Counsel, California Bay Area