We have had this problem at our hospital over and over, especially with teen 
moms. The doctors seem to believe that women can't take control of their own 
fertility.
I don't know if this helps but it's from a CEU course I wrote last year:

...Prolactin levels rise from a nonpregnant baseline of 10-25 ng/
mL to 200-400 ng/mL at term (Riordan and Auerbach 98).
Progesterone antagonism from the placenta enables the
prolactin level to rise without subsequent milk production
(Lawrence and Lawrence 65). Progesterone interferes with
prolactin’s activity on the cell receptor sites in the alveoli of
the breast (Riordan and Auerbach 98). With the birth of the
placenta, and the sudden drop in pregnancy hormones;
progesterone and estrogen, the elevated prolactin level brings
in the milk supply. Prolactin is released in pulses directly
related to stimulation of the areola or breast.
“For any hormone to exert its biologic effects, however,
specific receptors for the hormone must be present in the
target tissue (Lawrence and Lawrence 72).” Frequent feeding
in the early days increases the number of prolactin receptor
sites within the breast (Riordan and Auerbach 88). The
implication from research is that “the controlling factor in
breastmilk output is the number of prolactin receptors [in the
breast] rather than the amount of serum prolactin (Riordan
and Auerbach 101).” These prolactin receptors are laid down
in the first 3 months postpartum. The prolactin receptors in
the breast allow abundant milk production to continue when
total baseline prolactin levels drop over the first 3 to 4
months. Even with more “normal” baseline levels, breast
stimulation continues the doubling of the declining baseline
prolactin levels into the second year (Lawrence and Lawrence
66- 70).
The prolactin receptor site theory raises serious concern
over progesterone laden birth control methods when started
within days of the birth. Depo-Provera (medroxyprogester-one
acetate) shots are often given immediately postpartum,
while the mother is still in the hospital. If progesterone is an
antagonist to prolactin, logic dictates that progesterone shots,
implants and pills would inhibit early establishment of milk
production (Lawrence and Lawrence 666).


Marie Davis, RN, IBCLC
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