Do peanuts during pregnancy cause allergies?

With a rising number of children showing signs of food allergies in the United States, it's natural to wonder whether something that happens during pregnancy may contribute to it. Unfortunately, the evidence still isn't clear one way or the other.

A new study in the Journal of Allergy and Clinical Immunology finds that children whose mothers ate peanut products during pregnancy were more likely to test positive for peanut allergies.

That doesn't mean, however, that these children will actually show allergic symptoms, since the test does not indicate the strength of reaction, said Dr. Scott Sicherer, study author and pediatrician at Mount Sinai School of Medicine.

Most of the children in the study have not yet ingested peanuts, so it's not known what whether they actually have negative reactions to peanut-containing foods, he said. The test merely indicates that the child could have a peanut allergy.

Another limitation of the study is that the researchers could not control or verify how much peanut the mothers actually ate.

Participants were 503 infants between 3 and 15 months of age. They all had likely milk or egg allergies or significant eczema, which are risk factors for peanut allergy.

Based on reports of peanut product consumption from the infants' mothers, the researchers found an association between how much peanut they had eaten and the likelihood of a positive test for peanut allergy in the child.

In the past, the American Academy of Pediatrics has wavered on the issue. The organization said in 2000 that pregnant and breastfeeding women should avoid peanuts if the infant had an increased risk of peanut allergies based on family history. But it scrapped that advice in 2008 because there wasn't enough evidence to back it up.

Large studies tend to find no effect of peanuts during pregnancy on allergy development, while some small studies such as this one suggest there might be a connection, Sicherer said.

Sicherer has had some patients who avoided peanuts but still have peanut-allergic kids, and others who ate peanuts and wonder whether that caused an allergy in the child.

"I would not tell parents to feel guilty about it," he said.

His bottom line for pregnant women: Eat a healthy diet. There's not enough evidence to support or caution against eating peanuts, so just do what's right for you.