[Tanya Marie Squirrel]

'Progesterone works in partnership with estrogen during a woman's menstrual cycle, preparing her for a possible pregnancy, and contributing to an increase in her breast size. Estrogen stimulates the growth of breast tissue while progesterone causes water retention' -
http://www.ehow.com/facts_5798630_progesterone-breast-growth.html

if water retention is what progesetrone does in breast, it would seem then the more water retained the more rounder/fuller the breast would become?