Preschool-aged girls whose mothers had relatively high urine levels of BPA during pregnancy scored worse but still within a normal range on behavior measures including anxiety and hyperactivity than other young girls.
The results are not conclusive and experts not involved in the study said factors other than BPA might explain the results. The researchers acknowledge that "considerable debate" remains about whether BPA is harmful, but say their findings should prompt additional research.
The researchers measured BPA in 244 Cincinnati-area mothers' urine twice during pregnancy and at childbirth. The women evaluated their children at age 3 using standard behavior questionnaires.
Nearly all women had measurable BPA levels, like most Americans. But increasingly high urine levels during pregnancy were linked with increasingly worse behavior in their daughters. Boys' behavior did not seem to be affected.
The researchers said if BPA can cause behavior changes that could pose academic and social problems for girls already at risk for those difficulties.
"These subtle shifts can actually have very dramatic implications at the population level," said Joe Braun, the lead author and a research fellow at Harvard's School of Public Health.
For every 10-fold increase in mothers' BPA levels, girls scored at least six points worse on the questionnaires.
The study was released online Monday in Pediatrics.
Linda Birnbaum, director of the National Institute of Environmental Health Sciences and the National Toxicology Program, said the study contributes important new evidence to "a growing database which suggests that BPA exposure can be associated with effects on human health."
Grants from that federal agency helped pay for the study.
The Food and Drug Administration has said that low-level BPA exposure appears to be safe. But the agency also says that because of recent scientific evidence, it has some concern about potential effects of BPA on the brain and behavior in fetuses, infants and small children. The FDA is continuing to study BPA exposure and supports efforts to minimize use in food containers.
BPA has many uses, and is found in some plastic bottles and coatings in metal food cans. It was widely used in plastic baby bottles and sippy cups but industry phased out that use.
Braun said it's possible that exposure to BPA during pregnancy interferes with fetal brain development, a theory suggested in other studies, and that could explain the behavior differences in his study. Why boys' behavior wasn't affected isn't clear. But BPA is thought to mimic the effects of estrogen, a female hormone.
The researchers evaluated other possible influences on children's behavior, including family income, education level and whether mothers were married, and still found an apparent link to BPA.
But Dr. Charles McKay, a BPA researcher and toxicologist with the Connecticut Poison Control Center, said the researchers failed to adequately measure factors other than BPA that could explain the results.
For example, there's no information on mothers' eating habits. That matters because mothers' higher BPA levels could have come from eating lots of canned foods instead of healthier less processed foods, which might have affected fetal brain development.
The American Chemistry Council, a trade group whose members include companies that use BPA, said the research "has significant shortcomings ... and the conclusions are of unknown relevance to public health."