In a new study of Cincinnati-area kids, girls exposed to higher levels of bisphenol A before birth had more behavioral problems and were more anxious and over-active than those only exposed to small amounts of the chemical.
The finding doesn't prove that moms who have more contact with BPA, which is used to make plastics and found in some food packaging and canned goods, are putting their daughters at risk.
Additionally, there was no link between the amount of BPA measured in pregnant women's urine and boys' later behavioral problems, or between levels of the chemical in kids themselves and their behavior.
Although almost all women and kids had traces of BPA in their urine, "The vast majority of our children were typically-developing children and didn't meet any clinical criteria for behavioral problems," said study author Joe Braun, from the Harvard School of Public Health in Boston.
One researcher not involved in the study called the link between BPA and girls' behavior "very preliminary."
"Other groups are going to have to replicate these findings to be able to strengthen the implications of this particular study," said Dr. Amir Miodovnik, who studies children's environmental health at The Mount Sinai Medical Center in New York.
Braun and his colleagues took urine samples from 244 pregnant women living in and around Cincinnati twice during their pregnancies, and again right after they gave birth, and measured BPA concentrations.
After that, the researchers measured BPA levels in the children each year. At age three, parents filled out a survey on kids' anxiety, depression, aggression and hyperactivity, as well as any behavioral problems or trouble controlling their emotions.
Almost all women had BPA in their urine, at an average concentration of two micrograms per liter. For every 10-fold increase in that concentration during pregnancy, girls, but not boys, had significantly higher scores on tests of anxiety and depression and had worse behavioral and emotional control.
On the surveys, where a score of 50 represents an average kid, those increases were between nine and 12 points, "a fairly sizable effect" that parents would probably be able to notice, Braun said.
That was after the researchers took into account whether moms were depressed during pregnancy, as well as their race, income, education and marital status.
Miodovnik estimated that a score of about 65 on the tests "would be in the concerning range."
A higher BPA concentration in kids' urine at ages one, two and three wasn't linked to behavioral or emotional problems, the researchers reported in Pediatrics.
IS IT CAUSE-AND-EFFECT?
The findings don't prove that BPA exposure in the womb causes behavioral problems, Braun said.
"It might be that women who are consuming more processed and packaged foods and more canned foods are also consuming less nutrients that are important for brain development," for example, he told Reuters Health.
Still, "There's a growing body of evidence... that really seems to suggest what you're exposed to and what happens during gestation can set you up on your life course," Braun said.
"The brain begins developing from very, very early in pregnancy. Disruption in development could have lasting effects across childhood and the lifetime."
BPA is thought to be an "endocrine disruptor," a chemical that mimics or interferes with naturally occurring hormones in the body. Canada and the European Union ban its use in baby bottles.
Braun thinks the effect seen in the study was limited to girls because BPA may interfere with only certain hormones, and boys and girls get exposed to different levels of hormones as they're developing in-utero.
MORE STUDIES NEEDED
Recent research has linked high BPA levels in the urine of adults with a greater risk for diabetes (see Reuters Health story of October 19, 2011), but questions remain about the cause-and-effect nature of all BPA-related findings in humans.
Most studies about BPA's effect on behavior in particular have been done in animals, Miodovnik said.
In the current report, he added, the researchers "still haven't explained why they would see these particular (areas) affected, how it works... there's no real explanation. It's suggestive, and all it's really saying is, we need to do more studies."
Although the researchers agree that more work is necessary to confirm any effects of low levels of BPA exposure, Braun said there are some steps that pregnant women can take in the meantime if they're worried about potential harms.
"For concerned parents, they can reduce their exposure by reducing or eliminating consumption of canned and packaged foods, while at the same time maintaining a healthy and balanced diet," he said.
Still, "It's difficult to avoid all the sources of exposure," Miodovnik said.
"While we know that some sources are canned foods and packaged foods, there might be sources we don't know about out there, so it's difficult to give clear advice other than, 'Sure, try to avoid canned foods.'"