Pregnant women who are exposed to glyphosate, a widely used herbicide, may face an increased risk of preterm births, according to one of the largest studies to date examining the link.

The study, led by NYU Langone Health and published in Environmental Pollution, showed that pregnant women with higher exposure to glyphosate, the active ingredient in the weedkiller Roundup, faced a significantly higher risk of going into spontaneous labor early. While previous research has linked glyphosate exposure to shorter pregnancies, the NYU study is one of the largest to examine exposure during pregnancy and preterm birth in humans.

“This study reinforces that glyphosate exposure during pregnancy is widespread and may be linked to preterm birth risk. Even modest associations matter because pregnancy is a sensitive window, and small risks can translate into large population impacts,” said Jessie Buckley, professor of epidemiology at the University of North Carolina at Chapel Hill, in an email.