“You have to give your baby a bottle of water every day or he will die!” I will never forget hearing the woman in the subway wailing that sentiment to a young mother trying to subtly breastfeed her tiny newborn. Apparently, the older woman had suggested the newborn might be thirsty in the 100-degree heat and that the mother should offer him a few sips of cool water rather than tucking him under a receiving blanket for a snack, to which the mother calmly responded she did not give her baby water. Considering the baby was several weeks old, it was obvious the woman’s hysteria was not entirely accurate. Was there any truth in it, though? Does the warning from pediatricians and researchers stating babies should receive nothing but breast milk for the first six months of life include water?

There is a considerable amount of debate among the “old wives” over the value of water for newborns, but there is no ambivalence in the medical community. Unless the baby suffers from specific medical conditions leading to severe dehydration or constipation, newborns should be given nothing but breast milk for the first six months of life, and that includes water. The only acceptable alternative to breast milk is commercial baby formula, and the medical community agrees baby formula should only be given when it is physically impossible for the mother to provide breast milk. During the first six months of life, breast milk provides all of the liquid a baby needs to thrive. Breast milk is the natural form of nutrition for infants and provides everything their bodies need in terms of nutrients and fluid. There is no need to supplement with anything else, including water.

Not only is water unnecessary for infants, but it can also actually be dangerous. Even just a few ounces of water can fill up a baby’s tiny belly, making him unwilling to eat the breast milk that he needs. This can lead to malnutrition and dangerous weight loss. In severe cases, giving water to babies under the age of six months, and even in some older babies, can lead to a condition called water intoxication. Water intoxication occurs when sodium and electrolyte levels drop too low. This condition can lead to seizures, coma, and even death. Water should only be introduced when a baby has reached six months of age and is beginning to eat foods other than breast milk, and that should be limited to no more than four ounces per day until the age of one year.

Source: Williams HG. And Not a Drop to Drink—Why Water is Harmful for Newborns. Breastfeeding Review: Professional Publication of the Nursing Mothers’ Association of Australia.