Why do our nipples and privates darken?
Our breasts/nipples and genital areas can darken with age and irritation (rubbing of garments or breastfeeding), but the main cause is hormonal changes. This explains why it darkens a lot during puberty and also with pregnancy, causing pigments in your skin.
This is similar to pigmentation on the face, which hormonal changes is a huge factor for many Asian women. Other types of pigmentary changes found during pregnancy include dark underarms, development of a dark line called linea nigra down the middle of the tummy, as well as the worsening of existing pigmentation such as freckles and birthmarks.