Nipples are made for one purpose in life: to feed a baby. During pregnancy, colostrum can leak from the nipples as early as the second trimester. Colostrum is produced in the breasts from the first weeks of conception through the first few days after birth.
Nipple discharge is different from colostrum but is common for both women who are and are not pregnant. Typically a plug is located behind the nipple to prevent discharge, but that plug may not hold back all fluid. Nipple discharge can look clear, white, yellow or green and be completely normal. Red or bloody nipple discharge is not normal and should be reported to a doctor immediately. If nipple discharge is brown or black, foul smelling or flowing freely without stimulation, medical attention should also be sought.
For women who are breastfeeding, nipple discharge is something that will last throughout the months of feeding. Even after baby is weaned from the breast, milk production could continue for several months.