Immediately after conception, the body begins to prepare for breastfeeding, and the milk duct system in your
breasts becomes fully developed sometime
during your
second trimester of pregnancy.
And, as the American Pregnancy Association points out, since your
breasts start to produce colostrum
during the
second trimester (a watery pre-milk for newborns), you might start leaking some discharge — especially when your
breasts are massaged or sexually stimulated.