Giving newborns water, in addition to formula or breast milk, is usually unnecessary and possibly dangerous, warn researchers from the federal Centers for Disease Control and Prevention.
The caution is based on the CDC's survey of 1,743 mothers--conducted in 1993 and published this month in the Archives of Pediatric and Adolescent Medicine--in which one-fourth said they gave their newborns water at least three times a week.
The survey was part of the Food and Drug Administration's Infant Feeding Practices Study, in which a sample of women nationwide was selected and questioned. They were followed from late pregnancy through their infants' first year.
Ingesting too much water puts a newborn at risk of "oral water intoxication," says Laurence Grummer-Strawn, acting chief of the Maternal and Child Health Nutrition Branch of the CDC and one of the researchers. The excess water dilutes the needed sodium in the blood, so that the body cannot function correctly.
Newborns are especially at risk, Grummer-Strawn adds, because their systems are not as efficient at filtering water as are those of older infants.
The study serves as a reminder to caregivers--such as baby sitters, grandparents and even parents--who probably wouldn't give a second thought to giving an infant water, thinking that it is among the safer liquids to drink.
The warning also gives credence to advice that pediatricians have dispensed for years, says Dr. Sajjad Yacoob, a pediatrician at Childrens Hospital Los Angeles and USC assistant clinical professor of pediatrics.
So what's the right age to begin giving water?
In general, Yacoob says, parents can begin giving plain water to their infants by about month four, based on their pediatricians' advice.
Getting individual advice from one's own doctor is wise, agrees Grummer-Strawn, because in very hot weather, for example, a pediatrician might prescribe water for a young infant. But even in very hot weather, Yacoob says, he usually advises parents to simply offer infants more formula or breast milk.
According to the American Academy of Pediatrics, plain water is usually not needed by infants until they begin to eat solid foods, usually at 4 to 6 months.
The first symptom of oral water intoxication, Yacoob says, might be lethargy, which a parent might pass off as unimportant. Other symptoms: paler-than-usual skin, altered mental state, bloating, abnormally low body temperature and seizures.
How little water might be dangerous for a newborn?
"No one has established safe thresholds," says Grummer-Strawn, whose study did not track illness in newborns given water. But based on his clinical experience, Yacoob says that "giving [a newborn] 2 or 3 ounces consistently, twice a day for a week or so, is enough to cause problems."