Midpregnancy herbicide exposure linked to increased risk of preterm birth

Exposure to a widely used herbicide during the middle months of pregnancy may increase the chance of giving birth too early, before 37 weeks, a new study shows.

The investigation focused on glyphosate, the active chemical ingredient in professional-grade Roundup products, which are sprayed on commercial food crops, like grains and legumes, and on residential gardens. Residues of the chemical have been detected in cereals, snack foods, and fresh fruits and vegetables.

Led by NYU Langone Health researchers, the new study, which included 1,450 women, revealed that those with higher levels of glyphosate in urine samples collected during midpregnancy were more likely to go into spontaneous labor before 37 weeks than those with lower amounts of the herbicide.

This pattern was not seen when glyphosate was measured in the first few months of pregnancy. The study also found no link between the chemical and early births prompted by physicians for medical reasons, such as preeclampsia or poor fetal growth.

Past research has linked heavy use of the herbicide among farmworkers to non-Hodgkin lymphoma and other health concerns, but less is understood about everyday exposure, such as from eating foods with traces of the herbicide. More than 80 percent of Americans likely have detectable levels of the herbicide in their urine, according to the Centers for Disease Control and Prevention.

Our findings add to a growing body of evidence that exposure to glyphosate early in life may lead to health concerns that can echo throughout a lifetime."

Teresa Herrera, MPH, study lead author, doctoral candidate, Department of Population Health, NYU Grossman School of Medicine

Preterm birth is a leading cause of illness and death in newborns, and premature babies face higher risks of breathing problems, infections, and long-term learning and developmental challenges.

Laboratory studies in animals and cells have suggested that glyphosate might trigger inflammatory mechanisms that could lead to early labor. However, earlier investigations in humans have been small or inconsistent, and few have measured the herbicide at multiple time points in pregnancy, said Herrera.

Published online July 14 in the journal Environmental Pollution, the new work is among the largest study to date examining glyphosate exposure during pregnancy and preterm birth in humans. It is also among a select few to measure the chemical at more than one point in pregnancy, according to the authors.

For the analysis, the research team used data from the Children's Health and Environment Study, which tracks families' health from pregnancy through childhood. Women in the study were planning to deliver at NYU Langone–affiliated hospitals in New York City between 2016 and 2019. They provided urine samples once between four and 17 weeks of pregnancy and again between 18 and 25 weeks.

The team reviewed medical records to see how far along each woman was at delivery and whether any early births were spontaneous or medically induced. Their statistical models also considered other factors that can affect preterm birth risk, such as age, past experiences during pregnancy, and education.

By separating spontaneous from medically induced cases, the researchers found that glyphosate's effects seemed more closely tied to mechanisms that trigger labor on their own, such as inflammation, than to medical problems that lead clinicians to induce labor or perform an early cesarean section.

According to Herrera, families concerned about herbicides may want to choose organic grains and produce when possible and discuss questions with their healthcare providers. At the same time, because the herbicide is so widespread in the environment, individual choices alone are unlikely to eliminate exposure, she cautioned.

"These results underscore the need for stronger regulations to protect the health of pregnant women and infants, two groups long known to be especially vulnerable to chemicals in the environment," said study senior author Leonardo Trasande, MD, MPP, the Jim G. Hendrick, MD, Professor of Pediatrics at NYU Grossman School of Medicine. "Organic farming methods can produce competitive yields, so the trade-off between weed control and long-term health risks is not as straightforward as is often portrayed."

Dr. Trasande, who is also a professor in the Department of Population Health and director of NYU Grossman School of Medicine's Division of Environmental Pediatrics and Center for the Investigation of Environmental Hazards, cautioned that the analysis cannot prove that glyphosate directly causes preterm birth.

The researchers next plan to examine the mechanisms through which glyphosate exposure may affect fetal development and birth.

Funding for the study was provided by National Institutes of Health grants R01ES032214 and ES036249.

Dr. Trasande has received travel reimbursement support from the Endocrine Society, the World Health Organization, the United Nations Environment Programme, Japan Environment and Health Ministries, and the American Academy of Pediatrics. He also serves as a board member of Beautycounter, Ahimsa, Grassroots Environmental Education and Footprint. None of these activities were related to the current study. The terms and conditions of all these relationships are being managed by NYU Langone Health.

Along with Herrera and Dr. Trasande, NYU Langone researchers involved in the study were Whitney Cowell, PhD, MPH; Kim Cajachagua Torres, MD, PhD; Natasha Ard, MD; Kurunthachalam Kannan, PhD; Zhongmin Li, PhD; Shilpi Mehta-Lee, MD; Mengling Liu, PhD; and Akhgar Ghassabian, MD, PhD. Other study co-investigators include Fiona Fragomen at Case Western Reserve University and Heather Burris, MD, MPH, at the University of Pennsylvania.