Allergies in Pregnancy
Questions first arise during pregnancy, when a mother-to-be in a family with allergies starts to think about the food she eats and the effect on her fetus. She is likely to wonder: will succumbing to late-night cravings for peanut butter cups mean my child will be burdened with anaphylaxis to that legume? It’s still common for general practitioners to counsel pregnant patients to avoid highly allergenic foods in the last trimester. But there is a gulf between that advice and what scientists in the know believe is necessary.
For instance, Cyr says, “There’s little evidence that avoiding nuts or allergenic foods in pregnancy is helpful. A lot of people still say it. We don’t have evidence that says it’s harmful.”
So little has been proven definitively that perhaps even the precautions an expecting mother takes to minimize the risk of allergy – such as avoiding peanuts – might in fact make the fetus more susceptible. “It is possible that avoiding peanuts is harmful,” says Cyr, an investigator working with AllerGen, the federally funded allergy research network. Peanut exposure might actually mitigate against allergy. The fact is, scientists do not yet know.
So what’s a parent to do? “Just do what you know is good for your baby,” advises Dr. Michael Kramer, Scientific Director of the Institute of Human Development, Child and Youth Health (one of the government of Canada’s CIHR research institutes, as well as a professor at McGill University in the departments of pediatrics and epidemiology, biostatstics and occupational health.
And that, he says, is exclusive breastfeeding for six months and then for as long as the mother and child are comfortable after that. “That’s one thing we know she (the mother) can do for her child’s health.” Kramer is the principal investigator of a long-term study out of Belarus that is tracking the offspring of several thousand women for what the research team hopes will be several decades. Breastfeeding and asthma and allergy the risk of atopic dermatitis (eczema) or at least afford some protection from it in the first year, says Kramer.
But a mother’s milk does not guarantee an allergy-free future. In 2002, Sears (now head of the CHILD project) and some colleagues released results from a long-running birth cohort study in Dunedin, New Zealand. From the time they were age 9 until they were 26, every two to five years the participants in that group were tested for allergies and their lung function was a d. In the 2002 report, Sears and his team used data from this study to analyze the relationship between breastfeeding and allergies. To the surprise of many in the medical community, the group who had been breastfed proved more likely to have asthma from age 9 onward than those who had been breastfed for four weeks or less. From the age of 13, the breastfed group also showed more allergy and asthma to cats and to dust mites.
California scientists also suggest in a 2006 review of studies that whether breastfeeding has a protective or sensitizing effect may depend on the mother’s own genetics. Meantime, a British scientific review noted that, “the jury is still out as to whether breastfeeding protects or not against the development of allergic disease.” None of this, however, makes breastfeeding any less than a good thing. Both Kramer and Dr. Mark Greenwald, chair of the medical and scientific committee of the Asthma Society of Canada, stress the dozens of health advantages to feeding a baby mother’s milk. These range from assisting cognitive development to reducing the risk of numerous chronic diseases. Greenwald says that all health issues considered, the benefits of breastfeeding far outweigh any risk of developing allergies. “With breastfeeding, I will not tell them to do anything in terms of restricting their diet,” says allergist Dr. Zave Chad.
The proteins in the foods a mother eats have been shown to make it into her breast milk. So the new mother might worry about whether those tree nuts or peanuts she ate a few hours before her baby’s feed might sensitize her child. “You can demonstrate peanut allergen in breast milk,” says Cyr. “But again, whether that increases the risk (of allergy) is debatable.”
Allergists across North America have been taking note of study findings that have sparked the debate. Dr. Zave Chad, president of the allergy section of the Canadian Paediatric Society and an Ottawa allergist, says that faced with pregnant patients with allergies in the family: “I don’t change their diets at all. With breastfeeding, I will not tell them to do anything in terms of restricting their diet.” He’ll make one exception with breastfeeding: “If a woman has another child with peanut allergy and she’s really worried about it, I might say to exclude peanuts. Even then, I will tell her that it’s not based on any evidence.”
Another contentious subject is the topic of “when” to introduce certain solid foods to a baby at risk of food allergy Many pediatricians and family doctors have been telling parents to follow the guidelines set out by the American Academy of Pediatrics. These recommend that the at-risk child not be fed dairy products until after the age of 1, eggs until after the age of 2 and that parents avoid giving the child tree nuts, peanuts or fish until the age of 3.
But allergy specialists, who also work with new mothers, point out that these guidelines come with no guarantees. They say the theories behind these recommendations are not rooted in science. “It’s more than mumbo-jumbo, it’s a mess,” says Dr. Milton Gold, a staff member in the Division of Immunology and Allergy at the Hospital for Sick Children and author of The Complete Kids Allergy and Asthma Guide. The logic behind withholding peanuts from at-risk children until they are 3 years old is based on the fact that many infants will outgrow allergies to milk and eggs by the age of 3. “Because of that, people felt that age 3 was probably OK for peanuts,” says Gold. “That’s all it is.”
From the lab, Cyr agrees that “the evidence underlying these guidelines isn’t great.” He cites studies that have resulted in conflicting conclusions. “My recommendation is that you should breastfeed. After that, I don’t have strong feelings about when you can introduce peanut and egg, just because of the controversy in the (medical) literature.”
Adding to the confusion, in July 2006, the American College of Allergy, Asthma and Immunology issued a consensus statement suggesting that it was “prudent” to prolong the delay of potentially allergenic solids in young children at risk of allergies – and then it offered a list of ages or introducing eggs, peanuts and seafood that mirrors the AAP guidelines. The statement prompted the food allergy experts from the Mount Sinai School of Medicine and the Duke University Medical Center to write a letter protesting that the recommendations were too definitive and “not a logical conclusion of the material presented.” The letter noted that some studies suggested extended avoidance of certain solid foods might even increase the risk of atopic ‘It’s more than mumbo- jumbo, it’s a mess,” Dr. Milton Gold says of the age guidelines on introducing solid foods. disease. “Everyone wants to say: ‘Do this to make it better,” says Dr. Scott Sicherer, an allergist and associate professor at Mount Sinai. “But what if you don’t know that doing this is going to make it better?” Given the lack of clarity, in Canada, Chad and his colleagues at the pediatric and allergy societies are developing a position paper on infants and allergies. Chad says it is not likely to uphold the precise ages for introducing potentially allergenic solids. In the United States, the AAP guidelines are also being reviewed.
Thankfully, there is at least consensus on one aspect of giving food to children at risk of allergy The experts agree that, after four to six months of exclusive breastfeeding, solid foods may be introduced. Doctors want to avoid solids before the digestive system has had some time to mature.
Regardless of whether food allergies run in the family, parents are advised to start some foods before others. In North America, rice cereal is a child’s first taste of food other than milk, followed by grains like barley and oats and then green vegetables and yellow vegetables such as carrots, sweet potatoes and squash. Pediatricians also recommend feeding all babies only one new food at a time over a period of every few days – to make sure a child isn’t showing signs of an allergic reaction to the new food.
Next: Testing and Precautions