Probiotics, which encourage good bacteria to take up residence in the digestive system, may discourage the development of allergies, said Dr. Leonard Bielory, an allergist and immunologist now at the Center for Environmental Prediction at Rutgers University in New Jersey. Bielory was the primary investigator in a meta-analysis that suggested children may not be as allergic "if they have probiotics introduced into the diet or the mother's diet while pregnant."
Doctors are of one mind when it comes to pregnant women avoiding unpasteurized milk products, deli meats, raw fish and raw meats, which can lead to infections that could permanently affect the development of the unborn baby "and in some cases can be life-threatening," said Dr. Ari Brown, a pediatrician in Austin, Texas, and co-author of "Baby 411."
Beyond that, doctors tend to be more selective. Leo, for example, asks pregnant mothers who have a child with a documented food allergy "to avoid peanuts and tree nuts during the last trimester of pregnancy and during nursing if it's feasible. The data is still variable on this, but I feel this is a reasonable precaution for now in light of current studies."
Bielory said there are well-done studies coming down on both sides of whether early exposure to peanuts protects against allergies or makes children more vulnerable. He cited a recent study that showed in Israel, where "there's a lot of peanut-based products introduced early in childhood, they have a lower prevalence of peanut allergy, where as in the U.K., where they did adopt a ban on ingestion of peanut-based products in infants and children, there was interestingly a higher prevalence of peanut-associated allergic responses."
"It is hard to know what is right or if there is any definitive influence," Sicherer said.
He added he's had mothers say they ate lots of peanuts and thought it caused their child's allergies, while other mothers who avoided peanuts are stumped as to why their child is allergic to peanuts.
"I think that we, unfortunately, have to say we do not yet know a certain answer," he said
Most of all, Sicherer said he doesn't want his study to make mothers feel guilty about their past eating decisions.
"Our study says we need to look more carefully," he said, "but we are not prepared to change public health recommendations."