The reason women who don’t have babies do not see the nipple discharge on a regular occasion is because small pieces of breast tissue block the nipple ducts which keep the fluid within the breast instead of seeing lactation.

After becoming pregnant, the tissue is released to allow for lactation, in turn making it possible to breastfeed. Once breastfeeding has not been done for some time, tissue grows behind the nipple duct again, keeping nipple discharge from happening.

The most common reason for nipple discharge if not pregnant, is due to fondling or sucking of the breasts as well as irritation from clothing while being active. Drugs and hormone supplements are known to produce nipple discharge spontaneously and pituitary tumors can produce a milky nipple discharge.