Glyphosate in Pregnancy: What the Preterm Birth Study Found
A headline about weed killer and premature birth is a hard thing to read while you're pregnant. The study behind that headline is careful work, and what it measured is narrower than the headline suggests. Both of those things can be true, so let's go through it properly.
What the study measured
Researchers at NYU followed 1,450 pregnancies in New York City between 2016 and 2019. Each participant gave a urine sample early on, between 4 and 18 weeks, and a second one in the middle stretch, between 18 and 25 weeks. Both samples were tested for glyphosate and for AMPA, the compound glyphosate breaks down into. Seven percent of the babies, 103 of them, were born before 37 weeks.
Higher glyphosate in the mid-pregnancy sample came with higher odds of preterm birth, at an odds ratio of 1.35 (95% CI 1.04 to 1.76). Put simply, roughly a third higher odds. For spontaneous preterm birth specifically, meaning labor that started on its own rather than a delivery scheduled for a medical reason, the odds ratio was 2.01 (95% CI 1.40 to 2.90), or about double.
Three details limit what you can conclude from this result. The association showed up only in the mid-pregnancy sample and not the early one. AMPA showed no association with preterm birth in any model the researchers ran. And this is an observational study, so it can show that two things occurred together in this group of pregnancies. It cannot show that one caused the other, and the authors say so directly.
What other studies of glyphosate in pregnancy have found
A separate birth cohort in Puerto Rico measured hormones alongside glyphosate in 752 pregnancies. Higher glyphosate and AMPA came with lower estriol, an estrogen that rises through pregnancy, by roughly 8 to 11 percent. AMPA tracked with slightly higher T3, a thyroid hormone, and glyphosate with higher CRH late in the second trimester. The authors describe these as hormone systems the body relies on to maintain a pregnancy. That's a plausible route from exposure to outcome, and so far nobody has shown that it is the route.
Other studies have found less consistent results. A pilot study of 300 pregnancies in Illinois found glyphosate and AMPA tracking with slightly smaller babies and other differences in newborn measurements, yet the authors themselves called most of the findings imprecise, meaning the confidence intervals were wide enough that chance could explain the results. That's an ordinary state of affairs in environmental health research, where nearly everyone is exposed in small amounts that are hard to measure.
Which raises the practical question: can you change your own level? Partly. When four American families ate a fully organic diet for six days, urinary glyphosate dropped about 71%, and it fell to its new baseline within three days. That study had 16 people in it.
The trial in pregnant participants had a more sobering result. Thirty-nine pregnant participants were randomized to a week of conventional groceries and a week of organic groceries. Among those living more than half a kilometer from agricultural fields, about a third of a mile, glyphosate came down modestly. Among those living closer to fields, a week of organic food made no difference at all. Diet is one route in. For some people it isn't the main one.
Where to put your effort
I spend a lot of my week talking with people about environmental load, especially patients with mast cell activation and chemical sensitivity, for whom the question is constant and often frightening. What I've come to think is that the most useful approach to environmental exposures is a proportionate one. You cannot filter the whole world. You can change a handful of things that cost you little and reduce exposure measurably, and then you can stop spending energy on the question.
For glyphosate specifically, that means the exposures you control directly. Herbicide you or a neighbor applies to a lawn or a garden is a controllable exposure, and skipping it during pregnancy costs nothing but a few weeds. Where diet is the main route, meaning you don't live beside sprayed fields, choosing organic for the foods you eat most often lowers your level within days. Those two moves are cheap, and both come out of trials rather than out of theory.
The rest of it belongs with your prenatal team. The preterm birth risk factors with the strongest evidence behind them, things like a previous preterm birth, smoking, and untreated infection, are already what routine prenatal care screens for. Those conversations do more for your pregnancy outcome than any single grocery decision will.
What you can do about glyphosate while you're pregnant
One observational study found an association between mid-pregnancy glyphosate and preterm birth. It's a well-conducted study, and it doesn't establish cause.
The pathway is biologically plausible, given a second cohort found glyphosate tracking with hormone changes relevant to maintaining a pregnancy. Plausible is not proven.
Diet is one exposure route. Living near sprayed farmland is another, and in the pregnancy trial, living close to fields canceled out the effect of changing diet.
Skip herbicide use at home while you're pregnant. It's the easiest exposure to remove and it's free.
If organic groceries fit your budget, prioritize the foods you eat most often. Levels shift within about three days, so consistency does more than perfection.
Bring the worry to your prenatal appointments rather than to search results at midnight. Your team can tell you which risks apply to your specific pregnancy.
A pregnancy spent afraid of the grocery store isn't the goal, and fear is a poor guide to deciding which changes to make. Two or three deliberate changes, made calmly, do more than a hundred anxious ones.
References
Herrera T, Fragoman F, Ghassabian A, et al. Associations of glyphosate exposure in pregnancy with preterm birth: a longitudinal birth cohort study. Environmental Pollution. 2026;408:128775. PMID 42448271. doi:10.1016/j.envpol.2026.128775
Valentín-Cortés MA, Cathey AL, Jenkins HM, et al. Glyphosate exposure and hormonal disruption in pregnancy: evidence from a birth cohort in Puerto Rico. Journal of Exposure Science & Environmental Epidemiology. 2026. PMID 42297896. doi:10.1038/s41370-026-00902-6
Morris KA, Cinzori ME, Ryva BA, et al. Associations of glyphosate and aminomethylphosphonic acid (AMPA) concentrations with birth outcomes in pregnant women from the Midwestern U.S. International Journal of Hygiene and Environmental Health. 2025;272:114733. PMID 41401588. doi:10.1016/j.ijheh.2025.114733
Fagan J, Bohlen L, Patton S, Klein K. Organic diet intervention significantly reduces urinary glyphosate levels in U.S. children and adults. Environmental Research. 2020. PMID 32797996
Hyland C, Bradshaw PT, Deardorff J, et al. Urinary glyphosate concentrations among pregnant participants in a randomized, crossover trial of organic and conventional diets. Environmental Health Perspectives. 2023. PMID 37493357. doi:10.1289/EHP12155
NYU Langone Health. Exposure to weed killer during pregnancy may increase risk of preterm birth. Press release, July 2026. https://nyulangone.org/news/exposure-weed-killer-during-pregnancy-may-increase-risk-preterm-birth (secondary source; the peer-reviewed study at reference 1 is the primary citation)
All peer-reviewed citations were retrieved and verified through PubMed.
A note on how to use this
This article is educational and isn't medical advice. Pregnancy care is individual, and nothing here can account for your history, your medications, or your circumstances. Please bring any concerns about exposures or preterm birth risk to the provider managing your pregnancy, who can tell you what applies to you specifically.
If this resonates with what you're experiencing and you'd like to explore a naturopathic approach, book a consultation with our clinic.
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