it is not necessary to wash your nipples with soap water, which usually dry out the skin. It is same as you usually don't wash your lips with soap. In fact, the oil gland within the nipple help to moisturize the areola area. If you do want to put something on your nipples, you can talk to your doctor. The major issue around the breast care is to make sure your nipples stand out under stimulation. Women who have flat nipples or inverted nipples usually could not form the protrusion for their babies to latch on.(it does not mean those women could not have successful breastfeeding). and they would be recommended to have their breast care/nipple care during pregnancy. If you have flat or inverted nipples, you should talk to your doctor.