In what they claim is the first prospective birth cohort study of its kind, U.S. researchers have linked likely environmental and dietary exposure to glyphosate (N-phosphonomethylglycine), the most heavily used herbicide worldwide, with shorter pregnancies. The study, by researchers at Indiana University and the University of California San Francisco (UCSF), found that 93% of a cohort of pregnant women in the central Indiana region had detectable urine levels of glyphosate— the active ingredient in the herbicide Roundup®—which correlated with reduced gestation time. While glyphosate wasn’t identified in any samples of drinking water tested, higher urine glyphosate levels were found in pregnant women who lived in rural areas, and also in those who consumed more caffeinated beverages.
“One thing we cannot deny is that glyphosate exposure in pregnant women is real,” says lead investigator Shahid Parvez, Ph.D., an assistant professor in the department of environmental health science at the Indiana University Richard M. Fairbanks School of Public Health. “The good news is that the public drinking water supply may not be the primary source of glyphosate exposure, as we initially anticipated.…It is likely that glyphosate is eliminated in the water-treatment process. The bad news is that the dietary intake of genetically modified food items and caffeinated beverages is suspected to be the main source of glyphosate intake.”
The researchers report their findings in the journal Environmental Health, in a paper entitled, “Glyphosate Exposure in Pregnancy and Shortened Gestational Length: A Prospective Indiana Birth Cohort Study.”
Glyphosate is a broad-spectrum phosphate herbicide, and the most heavily used globally, the researchers note. Use is particularly heavy in the Midwest region of the U.S. due to corn and soybean production. Crops that have been genetically modified to be resistant to glyphosate have residues of the herbicide. “Over 90% of corn, soy and canola grown in the United States are modified in this way, and these grains are used in most process foods,” the authors write.
In utero exposure to relatively high concentrations of Roundup or its active component glyphosate has been associated with birth defects and fetal loss in a range of animals. Even low doses have been linked with fetal abnormalities and late embryonic deaths, the authors note. Biochemically, the herbicide has been shown to disrupt developmental and enzymatic pathways, and also cause DNA and chromosomal damage. However, the researchers point out, “Despite evidence of potential genotoxicity and teratogenic activity of GLY [glyphosate] in animal studies, GLY effects on human pregnancy and fetal development have not been investigated.…Current evidence for an association between GLY exposure and elevated risk of adverse reproductive and developmental outcomes is limited and inconsistent.”
The researchers designed a prospective birth-cohort study to test the hypothesis “that GLY can be directly measured in the urine of most despite evidence of potential genotoxicity and teratogenic of contaminated food, beverages, and drinking water, and that higher GLY levels in pregnancy will correlate with adverse fetal outcomes.”
Their study included 71 pregnant women, average age 29 years, from nine counties in central Indiana. Participants lived in rural, suburban, and urban environments. Urine and residential drinking water samples were obtained while the women received routine prenatal care, and glyphosate levels measured using liquid chromatography-tandem mass spectrometry. The women also filled out a questionnaire about food and water consumption, while maternal risk factors and neonatal outcomes were gathered from medical records.
Detectable levels of glyphosate were found in 66 out of 71 (93%) of urine samples, but surprisingly, the study results indicated that drinking water wasn't the source, as the chemical wasn’t detected in any of the drinking water samples. Rather, maternal area of residence and caffeine consumption were the only two variables that were significantly associated with the amount of glyphosate found in urine. Substantially higher levels of the herbicide were found in the urine of women who lived in rural environments, or who consumed <24 oz. of caffeine per day.
The authors point out that prior research has suggested that the most likely primary sources of exposure to glyphosate are dietary. The European Food Safety Authority and the Canadian Food Inspection Agency, for example, have separately identified glyphosate in various foodstuffs, including pulses, beans, and grains, as well as coffee beans, tea, and mushrooms, infant cereal and baby food, as well as juices and processed forms of fruits and vegetables, the team notes. “Recently, the Food and Drug Administration (FDA) began preliminary testing of samples of soybeans, corn, milk, and eggs for glyphosate residues in 2017, which implies that these commodities may have residual GLY,” they add.
The study results also pointed to a small, but significant correlation between glyphosate exposure and shorter pregnancies. “This study reinforces a growing body of evidence suggesting that pesticide exposure in pregnancy may be correlated with gestational length, as well as adverse fetal growth,” the researchers write. And as Dr. Parvez adds, “Although our study cohort was small and regional and had limited racial or ethnic diversity, it provides direct evidence of maternal glyphosate exposure and a significant correlation with shortened pregnancy….There is growing evidence that even a slight reduction in gestational length can lead to lifelong adverse consequences.”
Given the correlation between shorter gestation time and glyphosate exposure highlighted in their relatively small study, the team hopes to continue their work in larger cohorts of women. “Preliminary testing of samples of soybeans, corn, milk, such as birth defects, miscarriage, preterm births, low birth weight, and small for gestational age will require much larger cohort sizes across diverse population,” the authors write. “We are planning, contingent upon funding, to conduct a more comprehensive study in a geographically and racially diverse pool of pregnant women to determine if our findings are the same,” Dr. Parvez comments.