There is no evidence to prove that children below three years of age who were given anaesthesia had lower intelligence level than those who did not have it, say researchers.
In 2016, US Food and Drug Administration (FDA) had warned that prolonged or repeated sedation before age three may affect brain development.
However, the warning was based largely on data from animals, which may or may not apply to children, said the researchers from Mayo Clinic in Minnesota.
The new study, published in the journal Anaesthesiology, showed that intelligence, memory and several other measures of brain function were similar among those who received anaesthesia and did not.
"For the majority of kids undergoing surgery, the results overall are reassuring," said lead author David Warner, a paediatric anaesthesiologist at Mayo Clinic.
"About 80 percent of kids who need surgery under age three only need one and it's relatively brief," he added.
However, for those with multiple exposures to anaesthesia had modest declines in fine motor skills, but their parents reported more learning and behavioural problems.
Parents whose children had anaesthesia once under age 3 reported more problems with mental skills known as executive functions -- skills that help with memory, impulse control, planning and flexibility -- but not with other behaviours, the findings showed.
For the study, the team studied 997 people who had anaesthesia exposures before their third birthdays.
Beyond their anaesthesia exposure, the three groups of patients were matched to be as similar as possible, the results revealed.
Several other studies also show little evidence that a single anaesthetic is associated with significant harm.
"Although we do have some concerns about the children who are receiving multiple anaesthetics, it's important to note that our results don't allow us to conclude that anaesthesia itself is causing problems," Warner said, adding that other factors, such as the conditions that make surgery necessary, could contribute.
"However, the fact that we found some problems in some of these children means that research in this area needs to continue, including further analysis of our data," he added.