Around 3rd trimester with my first. I never leaked much, maybe the tiniest droplets when I curiously squeezed to see what was there. It wasn't really indicative of anything, though, because my supply has always been pretty bonkers despite how little breast change I had during pregnancy. They definitely made up for it after my milk came in several days after giving birth, though. I thought I'd never stop fountaining from the "other" side during every nursing session.