The womb protects a developing fetus, but it might not be able to fend off air pollution. Researchers have presented a small study suggesting for the first time that air pollutants can make their way from a pregnant woman's lungs to her placenta, reports the Guardian. Because the placenta allows nutrients and oxygen to flow from the woman's blood stream to her fetus, that means it could similarly allow pollutants into the womb as well, per CNN. "Our evidence suggests that this is indeed possible," says Norrice Liu, a pediatrician who led the research at Queen Mary University in London. "We also know that the particles do not need to get into the baby's body to have an adverse effect, because if they have an effect on the placenta, this will have a direct impact on the fetus."
The study, presented at the European Respiratory Society International Congress in Paris, was indeed small, involving just five women. But researchers found "black sooty" particles, believed to be carbon, in the placentas of each one, says another of the researchers, Lisa Miyashita. Further analysis is in the works to confirm, but the results mirror similar ones in animals. Given previous research laying out the potential dangers that air pollution can cause to babies, the scientists say the study should factor into the advice given to pregnant women, even if it's as simple as wearing a mask or avoiding especially busy roads when out and about. The good news: All five of the women gave birth to healthy babies. (Air pollution might be the world's greatest killer.)