Giving your baby antibiotics too early may increase their chances of being overweight in childhood, new research suggests.
Specifically, infants exposed to antibiotics during the first six months of their lives are 22 percent more likely to be overweight between the ages of 10 months and 3 years -- though their weight tends to return to average by the time they are 7 -- according to a study published in the International Journal of Obesity on Tuesday.
This effect on the child's body mass appears to be dependent upon the timing of the antibiotics. The exposure to antibiotics later in childhood -- while the child is between six months and 3 years old -- is not associated with increased body mass.
Researchers say the reason for the weight gain could be that antibiotics at this tender age may change the delicate balance of bacteria in infants' digestive tracts.
"Unnecessary antibiotic use can disrupt healthy bacteria that live in our intestine," said Dr. Leonardo Trasande, primary study author and associate professor in pediatrics at New York University. "If we have a disruption in the microbes in this gut, it can lead to over-absorption of calories and obesity."
The study sample included 11,532 children from the United Kingdom whose parents agreed to the study before the babies were born. Researchers checked the height, weight and antibiotics use of these children at birth, and then after approximately 7 weeks, 10 months, 20 months, 38 months and 7 years.
The researchers also took into account other factors, such as the weight of a baby's parents, whether the mother smoked while pregnant, the parents' socioeconomic status and what the baby ate. Even when they did this, though, the relationship between antibiotic use in these infants and their weight gain remained.
"This will affect our thinking about the obesity epidemic," Trasande said. "This study suggests the need to shift the paradigm from thinking simply about diet and exercise to other environmental exposures."
Physicians were quick to note that this study does not mean that antibiotics should not be used in these infants when they are clearly needed. However, doctors said that all too often, antibiotics are used inappropriately -- and this practice can have real consequences for babies' health.
"I think that generally antibiotics are quick, frequently overused by practitioners to treat viral infection," said Dr. Richard J. Deckelbaum, professor of nutrition, pediatrics, and epidemiology at Columbia University Medical Center. "I think that practitioners have to be aware of these findings.
"It's fast to write a prescription rather that to wait through a viral infection. It's another cautionary paper about not overusing antibiotics in young children."