Final answer:
Washing nipples in the last trimester is part of prenatal hygiene practices in anticipation of breastfeeding, involving hormonal changes and colostrum production. It is important for preventing infection and promoting the health of the mother and infant.
Step-by-step explanation:
The use of water to wash the nipples in the last trimester pertains to the health and hygiene practices of an expecting mother in preparation for breastfeeding. The mammary glands undergo significant changes to prepare for lactation, indicated by the swelling of alveoli with colostrum, a nutrient-rich substance vital for a newborn's initial days. It is suggested to maintain cleanliness to prevent potential infections, as exemplified by Semmelweis's advocacy of handwashing to reduce puerperal fever instances, translating the importance of hygiene to a prenatal context.
While there is not a specific recommendation for nipple washing in the provided references, the implication of general hygiene is clear. The hormonal changes, leading to milk production triggered by prolactin, and milk ejection facilitated by oxytocin, indicate the importance of maintaining breast health. Additionally, as newborns have immature kidneys and require adequate hydration, the mother's preparation for breastfeeding, including hygiene practices, is critical.