[Dynsei]

That's directly from http://wikipedia.org/wiki/Prolactin
...
During pregnancy, high circulating concentrations of estrogen increase prolactin levels by 10- to 20-fold.

its progesterone, not estrogen. Wikipedia gets things wrong. Someone probably thought progesterone was an estrogen, and its not. Verification would be needed.

summarized from britannica, the corpus luteum is the temporary organ which produces progesterone, this progesterone, signals the pituitary gland to release prolactin, which also tries to hold on to the egg. [This is a loop, a reinforced signal]. If the egg (corpus luteum) is not fertilized, it stops producing progesterone, the pituitary gets this message, and stops raising prolactin. Progesterone and prolactin were putting estrogen's effects on hold.

The unfertilized egg is released, through menstruation, because of estrogen. If the egg is fertilized, this produces more progesterone. The pituitary and the placenta signal strongly in a loop to protect the baby from being aborted through menstruation.

I also know that estrogen lowers both prolactin and progesterone.

The rest of the quote seems correct.