When a newborn accidentally drinks water, it is a common concern that can become a serious medical issue. Infants under six months of age should not consume plain water, as breast milk or formula provides all the necessary hydration. A baby’s body is not yet equipped to safely process free water, which immediately raises the stakes for even small accidental intakes. The risks range from nutritional deficiency to a life-threatening condition called water intoxication.
Why Water is Dangerous for Newborns
The danger of giving water to an infant under six months stems from their immature kidneys, which cannot filter excess free water efficiently. A newborn’s kidneys struggle to excrete extra fluid, causing it to build up in the body. This inability to process water leads to a dilution of essential minerals in the bloodstream, resulting in water intoxication.
The most concerning result of this dilution is hyponatremia, a dangerously low level of sodium in the blood. Sodium is an electrolyte that regulates fluid balance, nerve signaling, and muscle function. When sodium levels drop too low, water moves from the bloodstream into the body’s cells, causing them to swell. This swelling is particularly dangerous for the brain.
Beyond the physiological risk, an infant’s small stomach fills quickly with water, displacing nutrient-dense breast milk or formula. This displacement deprives the baby of the calories, fats, and proteins required for rapid growth and development. Since breast milk is about 87% water and formula is about 85% water, additional plain water is unnecessary for hydration.
Recognizing Water Intoxication Symptoms
If a baby has consumed water, parents should be vigilant for signs of water intoxication, which is a medical emergency. Behavioral changes are often the first noticeable signs, such as unusual fussiness, irritability, or excessive sleepiness. These symptoms reflect the early stages of electrolyte imbalance affecting the central nervous system.
Physical symptoms can include puffiness or swelling in the face, hands, or legs, caused by the body retaining excess water. A drop in body temperature, sometimes below 97 degrees Fahrenheit, signals that the body’s regulatory systems are compromised. Nausea and vomiting may also occur as the imbalance progresses.
The most severe signs of hyponatremia are seizures, which manifest as sudden jerking movements, stiffening, or staring spells. Seizures indicate brain swelling and require immediate medical intervention. If a baby exhibits any of these symptoms after accidental water intake, parents must seek emergency care without delay.
When Water Becomes Safe
The transition point for safely introducing water typically occurs around six months of age, which is generally when solid foods are introduced. By this time, the kidneys have matured enough to handle small amounts of free water. The Centers for Disease Control and Prevention (CDC) suggests offering small amounts, generally four to eight ounces of water per day, at this stage.
Water should be offered in a cup, such as a soft-spout sippy cup, a straw cup, or an open cup, rather than a bottle. This method helps the baby develop new drinking skills and prevents them from filling up too quickly. Water should be supplemental and offered during mealtimes, not as a replacement for breast milk or formula.
Milk remains the primary source of nutrition and hydration for the first year of life. Until a baby’s first birthday, breast milk or formula should still make up the majority of their fluid intake. Water intake gradually increases as the baby consumes more solid food, but its role is to complement, not compete with, the milk supply.