The "low overall difference in academic performance after childhood exposure to surgery is reassuring," they write in JAMA Pediatrics.

Studying the health and school records of more than 2 million children born in Sweden between 1973 and 1993, the researchers identified 33,000 children who had one surgery with anesthesia before age four and 159,000 children who were similar in most ways but had not had surgery or anesthesia before age 16.

On average, kids who’d had anesthesia had 0.41 percent lower school grades at age 16 and 0.97 percent lower intelligence quotient (IQ) scores at age 18.

Kids who had been exposed to anesthesia two or three times before age four had school grades between one and two percent lower than the comparison group of kids, the authors report.

The difference was less than the impact of mother’s level of education, gender and even month of birth, said lead author Dr. Pia Glatz of Kalmar County Hospital in Sweden

Surgical management, the surgery itself and whatever caused the surgery to be necessary in the first place may also have played a role, although none of the children in this study had any serious medical diagnoses, the authors note.

“No child is exposed to anesthesia and surgery unless it is absolutely necessary,” Glatz told Reuters Health by email. “Necessary conditions could be serious malformation, inguinal hernia or urological conditions or ENT (ear-nose-throat) disorders with hearing impairment.”

Based on recent animal studies, anesthesia exposure may change brain development, but the doses and durations used in pediatric practice have not caused structural changes in the brains of animals, she said.

“Based on these findings, families and caregivers should not hesitate to provide surgery to young children when necessary, and the magnitude of any adverse effect of anesthesia and surgery should be interpreted in light of potential adverse effect by postponing surgery,” Glatz said. “We need to further understand whether there are certain high risk groups within the pediatric surgical population and if so, we need to come up with preventive strategies to avoid neurocognitive adverse effects in these children.”

The alternatives, i.e. postponing surgery, are most likely worse, said Dr. Tom G. Hansen of Odense University Hospital in Denmark, coauthor of an editorial accompanying the study.

“Surgeries in young children are urgent and important,” Hansen told Reuters Health by email.