Sicherer also qualified the findings by saying the study involved only families with allergy histories, so the findings might not apply to the general population. Also, he said the study is observational, which means it doesn't prove cause and effect.
Nevertheless, several experts called the results significant, but not practice-changing.
"This is an area that deserves more investigation and more studies," said Dr. Neeta Ogden, an adult and pediatric allergist in private practice in Closter, N.J. "I've suspected in my own clinical practice, based on anecdotal evidence, that there has been some association. A study like this puts it on our radar for pregnant women that perhaps they should be consuming peanuts with caution, especially when they're in their third trimester."
While it's clear that a mother's diet influences the health of her unborn child, there's a lack of evidence that eating specific foods can prevent certain illnesses and conditions in her child.
Said Dr. Stephen Wasserman, an asthma and allergy specialist at UC San Diego, "There is not going to be one diet or one set of behaviors for all people. People bring their genetics to the table and one person's good is another person's bad."
Doctors agree that pregnant women should aim for a well-balanced diet and make sure they get sufficient protein, which is the basis for a growing fetus' cells and tissues. But some go beyond that:
Some obstetricians and others urge mothers to eat fish rich in the omega-3 fatty acids thought to promote development of a healthy nervous system in the fetus. Most include the caveat that they need to avoid going overboard, because fatty fish also tend to have higher levels of mercury, which is toxic to immature brains.
A limited number of studies suggest a diet rich in vitamin D, the sunshine vitamin, may protect against allergies. Still, said Dr. Christian Pettker, medical director of labor and birth at Yale-New Haven Hospital, "we are actually learning that more and more women have vitamin D deficiency than we previously suspected For these reasons, more obstetricians are advocating a diet that accounts for a healthy amount of vitamin D, and if vitamin D deficiency is suspected, this should be looked into." However, said Dr. Harvey Leo, a pediatric allergist at the University of Michigan's Center for Managing Chronic Disease, because vitamin D is predominantly made by sun exposure, "a mother's diet may not make a difference at all. It may be the mother's sun exposure."
Both Omega-3 fatty acids and vitamin D decrease inflammation, and asthma and allergies are inflammatory disorders, so Dr. Katherine Sherif, Director of the Center for Women's Health and associate professor of internal medicine at Drexel University College of Medicine in Philadelphia, recommended pregnant women take Omega-3 supplements and vitamin D supplements daily.
Some studies suggest a Mediterranean diet rich in fresh fruits, vegetables, legumes and lean protein could protect against allergies. However, physicians who are sticklers for evidence, rather than anecdotes, say the benefits to the unborn child aren't proven. "The Mediterranean diet is sort of like vitamin C: It's probably not bad, but probably as many studies say it's beneficial as say it's not," said Dr. Dana Wallace, an allergist in Fort Lauderdale and the incoming president of the American College of Allergy, Asthma and Immunology.