The milk ducts in the breasts start to form in the period before your first menstrual cycle. These resemble a group of saplings and small branches. Right behind your nipple, separate groups of branches have started to form, and smaller branches are yet to grow out from these. After your menstrual cycle starts and in the ongoing process of growing, these ducts branch out even more and these branches grow buds and these milk-producing tissues enlarge immediately before a menstrual cycle, causing sensitivity in the breasts. 

The growing of branches accelerates during the first 3 months of pregnancy and new buds are added. Women realize they are pregnant mainly from the changes in their breasts. These changes feel different from the pre-menstrual sensitivity of the breasts and are of longer duration. Your breasts in this period are probably much more sensitive, and as more branches and buds are added, your breasts also start to grow, and this will become more noticeable in the further stages. From outside, you can see the formation of the blue veins going through your breasts, and the areola surrounding your nipples could have become darker and larger. 

Expectant mothers with inverted and flat nipples may experience difficulties in the first stage of breastfeeding. To prevent the pain and trauma caused by nursing the baby after delivery, an expectant mother can massage the nipple area for 15 seconds after his/her shower with a rough textured towel in circular motions, followed by the application of a softening cream. The massage will help toughen up the nipple and areola and prepare the breasts for nursing during pregnancy. 

Moving your breasts could be another important breastfeeding preparation you can implement during pregnancy. In particular, in some European countries, nurses suggest this method to expectant mothers. How to move the breasts? Open your hands like a dish under each breast and move your breasts gently up and down. Some sources indicate that toxins are eliminated and the sensitivity of breasts during pregnancy is reduced by moving the breasts 2 times a day as described here. 

Close to the end of your pregnancy, colostrum, the first and essential nutrient for the baby, starts to leak from the breasts in a few drops of dense and yellowish fluid. Colostrum leakage is possible. Faced with such circumstances, you can start using breast pads. If you don’t experience the above, it does not necessarily mean the absence of milk or that it will not be produced.  

If you do not have any health problems post-delivery, almost all mothers automatically start producing milk within a few days after the delivery.