We’re just beginning to learn about how diet in pregnancy affects asthma, eczema, and allergies in children. We know that over 90% of food allergies in young children are to one of five food: milk, eggs, peanuts, soy, or wheat. Some speculated that mothers’ avoiding these foods during pregnancy might reduce allergies.
But studies have not shown any preventive effect from avoiding these foods, expect perhaps for peanuts and maybe even other nuts. This may be worthwhile in families where allergies are a particular problem. However, the most important thing we know to avoid for allergy prevention is not a food, but tobacco smoke.
On the positive side of the diet, several studies show a significant benefit in preventing allergic disease by eating omega-3 fatty acids and eating the beneficial bacteria found in active culture yogurt.
You can find more information on this topic, including the references to these studies, in my book, From First Kicks to First Steps.