The purpose of a new study published in Breastfeeding Medicine was to describe changes in nipple skin and classify signs of nipple trauma in breastfeeding mothers during first week, postpartum.This study was conducted in two phases – phase-1 was an observational prospective study of breastfeeding mothers in which data were obtained from photographs and digital images of nipple skin,which were analyzed to anatomically classify signs of nipple trauma; in phase-2, the reliability of signs identified in phase-1 were verified. This study enrolled 50 breastfeeding mothers. The signs of nipple trauma included erythema, swelling, blistering, fissure, and scabbing. Purpura and peeling were identified only with photographic image analysis. Scabbing and blistering were classified as damage to the dermis, and erythema and swelling as damage to the epidermis, based on anatomical evidence and mothers subjective experiences of pain intensity. Erythema and swelling were observed from day 0; erythema was more frequent. Reliability was high for fissure, substantial for blistering and scabbing, and moderate for erythema and swelling. Hence, image analysis revealed five signs of nipple trauma. Erythema and swelling were the most frequently observed signs during postpartum week 1. Yet, the agreement rate was lower than that for other signs, suggesting the possibility of conflicting interpretations in clinical evaluation.