Pregnant women’s exposure to wildfire smoke — particularly in the third trimester — may increase the risk of autism in their children, according to new research, which looked at hundreds of thousands of births in Southern California.

The study, published Tuesday in the journal Environmental Science & Technology, is the first to examine a potential link between prenatal wildfire smoke exposure and autism. Earlier research has suggested that pregnant women’s exposure to air pollution more broadly, including smog spewed by vehicles, smoke stacks and lead, may be linked to the developmental disorder.