Babies who are exclusively breastfed usually do not need extra water because breastmilk contains a lot of water. If exclusively breastfeeding for a long time water may cause malnutrition to the baby, at the same time affect the mother lactation. 1. Malnutrition: Due to the limited volume of the baby’s stomach, if too much water is fed to the baby will make the baby feel full, thus affecting the baby’s breastfeeding amount. The baby can not absorb nutrients from breast milk, resulting in malnutrition, affecting the growth and development of the baby. 2. mother’s milk decreased: if the baby drank water, will inevitably reduce the number of times and amount of breastfeeding, the breast can not form an effective stimulus, will affect the amount of milk. If the baby long time to take pure breastfeeding water, growth and development slower than the same age children, it is recommended to timely medical care, under the guidance of the doctor, improve the relevant examination, clear cause, symptomatic treatment.