The official advice on this waxes and wanes, but currently, both the American Academy of Pediatrics (AAP) and the UK Food Standards Agency say that it’s fine to eat peanuts during pregnancy (even though both previously advised against it if there was a history of allergy or asthma in the child’s immediate family).
Certainly, several studies have suggested an indirect link between eating peanuts during pregnancy and childhood allergy. For example, in 2010, many newspapers seized upon an American study that found that children were more likely to test positive for antibodies against peanuts if their mothers had eaten peanut products during pregnancy (an indirect marker for possible peanut allergy). However, even the study’s authors urged caution in interpreting its results. For one thing, they relied on mothers’ memories of how many peanuts they had eaten, rather than measuring quantities themselves. They also tested only children who already had suspected allergies to milk or eggs rather than the general population, and they didn’t test for peanut allergy directly.
What’s more, several studies have found the opposite: that eating peanuts during pregnancy may protect infants against allergies. In such situations, the most sensible thing to do is to weigh the results of as many studies as possible to decide where the best evidence lies. Fortunately, someone has done this for us: In 2008, the American Academy of Pediatrics reviewed the available studies and concluded that there currently isn’t enough evidence to support the idea that avoiding peanuts—or other foods—during pregnancy will reduce your child’s risk of allergies. A recent review by the UK’s Committee on Toxicology reached a similar conclusion. This doesn’t necessarily mean peanuts have the all-clear; just that more good-quality research is needed to decide either way. Until then, you may as well carry on eating peanut butter—spread it on pickles, if you’d like.