It’s true that there are few published studies that focus on the effects of deet on pregnant women or their offspring, and almost none that examine deet usage during the first trimester when developing fetuses are most vulnerable.
It’s also true that there are some scary-sounding reports in both the research literature and the popular press. For example, at least one study found that when pregnant rats were exposed to high doses of deet, their offspring had low birth weights. At least three women who used deet during pregnancy gave birth to babies with severe birth defects, and at least one of those babies died.
But there are some important caveats to keep in mind when considering that information. First, the dose the rodents received was much higher than any normal human dose, and those findings about low birth weight were not replicated in other rat studies. In fact, similar animal studies found no effects from deet on pregnancy. Second, in the human cases, it’s very difficult to know whether deet was the true culprit.
The highest-quality research on deet in pregnant women is actually fairly reassuring.
Two separate studies—one in New Jersey (150 women) and one in Thailand (897 women)—found that while deet molecules can cross the placenta and enter the womb, they do so in very small concentrations. In both studies, babies born to mothers who used deet were not smaller or sicker and did not suffer from cognitive deficits or any major birth defects compared with babies born to mothers who did not use the chemical.
