A new study in rats has found that exposure to glyphosate during pregnancy and early life was associated with developmental effects not only in the offspring directly exposed, but in the following generation as well.
Researchers in Argentina followed two generations of rats after pregnant animals were exposed to either glyphosate alone or a commercial glyphosate-based herbicide.
Among the findings were altered fetal development, oxidative imbalance, reduced growth and increased mortality. The effects were generally more severe in the second generation, and male offspring appeared particularly vulnerable.
But one finding stands out for a much simpler reason.
The researchers detected glyphosate in the amniotic fluid surrounding developing fetuses.
In other words, glyphosate given to the mother reached the environment in which her unborn offspring were developing.
The study, published in Environmental Toxicology and Pharmacology, adds to a growing body of research asking whether pregnancy and early development may represent particularly important windows of vulnerability to glyphosate exposure.
What the study found
Researchers reported that:
- glyphosate was detectable in amniotic fluid;
- developmental and oxidative effects occurred across two generations;
- fetal growth restriction was observed in the second generation;
- male offspring appeared more vulnerable than females; and
- the commercial glyphosate-based herbicide generally produced more severe effects than glyphosate alone.
This was an animal study and does not establish that the same effects occur in humans.
What Did the Researchers Do?
The researchers used pregnant Wistar rats, dividing them into groups receiving either glyphosate, a commercial glyphosate-based herbicide, or a control treatment.
The exposed animals received the equivalent of 2 mg of glyphosate per kilogram of body weight per day, orally, beginning on day nine of pregnancy and continuing until their offspring were weaned.
Those offspring became the first, or F1, generation.
When the female F1 offspring reached adulthood, they were mated to produce another generation — F2.
This allowed researchers to look beyond the animals exposed while developing in their mothers and ask whether developmental effects were also apparent in their offspring.
They examined fetal growth, the placenta and amniotic fluid, markers associated with oxidative stress, postnatal growth and survival.
What they found was not confined to one generation.
Glyphosate Was Found in Amniotic Fluid
Perhaps the most immediately understandable finding was the detection of glyphosate in amniotic fluid.
Amniotic fluid surrounds and protects a developing fetus during pregnancy. Detecting glyphosate there demonstrated that glyphosate administered to the pregnant rats was able to reach the fetal environment.
The researchers describe this as confirmation of transplacental transfer.
That does not mean this study proves that precisely the same exposure occurs, or produces the same effects, during human pregnancy. This was a controlled animal experiment.
But it does establish something important within this model: maternal exposure did not necessarily mean exposure stopped with the mother.
The developing offspring were exposed too.
Effects Were Seen Across Two Generations
Researchers found changes associated with oxidative balance in the intrauterine environment in both generations.
Oxidative stress occurs when the normal balance between damaging reactive molecules and the body’s antioxidant defences is disrupted. During pregnancy, that balance matters because the placenta and developing fetus are undergoing rapid growth and change.
The researchers reported altered antioxidant enzyme activity and lipid peroxidation — a marker of oxidative damage — following exposure to both glyphosate and the glyphosate-based herbicide.
By the second generation, the researchers also found intrauterine growth restriction, meaning the F2 fetuses had not grown as much as expected during pregnancy.
After birth, differences continued.
Male offspring showed reduced body weight and increased mortality, particularly in the second generation.
Taken together, the researchers concluded that perinatal exposure to glyphosate or the glyphosate-based herbicide disrupted the oxidative balance of the intrauterine environment and produced adverse developmental outcomes across two successive generations.
Why Was the Second Generation Affected?
This is one of the most interesting questions raised by the research.
The F1 animals were directly exposed during their development because their mothers received glyphosate or glyphosate-based herbicide during pregnancy and lactation.
The F2 generation is different.
The F1 females were no longer being treated with glyphosate when they were mated to produce F2. Yet the researchers found developmental effects in that next generation — in some cases more pronounced than those seen in F1.
That does not automatically mean the study has demonstrated permanent genetic damage or that every future generation would be affected. Nor does it tell us precisely how the effects were carried from one generation to the next.
What it does show is that the consequences of exposure during a sensitive period of development did not necessarily end with the animals that experienced that exposure.
That is why multigenerational studies matter.
Male Offspring Appeared More Vulnerable
The effects were not identical between males and females.
The researchers reported sex-specific differences across the generations, with males generally showing greater vulnerability.
Reduced postnatal body weight and increased mortality were particularly evident among male offspring, and again the effects were more pronounced in the F2 generation.
Why males and females responded differently is not answered by this study. But sex-specific effects are important because toxicological studies that look only at combined results can potentially obscure effects that occur more strongly in one sex.
The Glyphosate-Based Herbicide Produced More Severe Effects
The researchers also did something particularly useful: they compared glyphosate itself with a commercial glyphosate-based herbicide.
That distinction matters.
Much of the toxicological evidence used to assess glyphosate concerns the active ingredient itself, while the herbicide products people actually use contain glyphosate alongside other ingredients designed to help the formulation perform effectively.
In this study, the commercial formulation generally produced more severe effects than glyphosate alone.
That doesn’t establish that every glyphosate-based herbicide is more toxic than glyphosate itself. Formulations differ, as do their other ingredients.
But it does reinforce an important question in pesticide safety assessment: is studying the active ingredient alone enough to understand the effects of the formulated product to which people and the environment are actually exposed?
This Isn’t the First Glyphosate Study to Find Effects in a Second Generation
The new research is particularly interesting because it doesn’t stand alone.
In October 2025, we reported on a separate study in mice examining prenatal glyphosate exposure. That research used glyphosate alone and found changes involving immune function, metabolism, the gut microbiome and behaviour that extended across two generations.
The studies are different. They used different animals, exposure protocols and biological measurements, and they should not be treated as though they are repetitions of the same experiment.
But both raise the same broader question:
Can exposure to glyphosate during pregnancy and early development have consequences that extend beyond the generation directly exposed?
You can read our article on the 2025 prenatal glyphosate study here.
With the new Argentine study, researchers have now reported multigenerational developmental effects using another experimental model and, importantly, have directly compared glyphosate with a commercial formulation.
But These Are Rats. What Does This Tell Us About People?
This study does not show that pregnant women exposed to glyphosate will experience the same effects, or that their children or grandchildren will.
Animal studies cannot establish that.
But that isn’t the same as saying animal studies don’t matter.
Rodents are routinely used in toxicology precisely because researchers cannot deliberately expose pregnant women and their unborn children to chemicals to see what happens. Animal studies allow scientists to investigate developmental processes, examine tissues and biological mechanisms, and follow effects across generations in ways that would be impossible or unethical in humans.
They are therefore used to identify potential hazards and questions that warrant further investigation — not to predict human outcomes with certainty.
We’ve looked more closely at that issue in We’re Not Rats… But Maybe We Should Pay Attention Anyway, including why animal studies remain an important part of chemical safety science.
Why Pregnancy and Early-Life Exposure Deserve Particular Attention
An adult body and a developing fetus are not simply smaller and larger versions of the same thing.
During pregnancy, cells are dividing rapidly, organs are forming and biological systems are being programmed for later life. Disruption during those developmental windows can potentially have consequences quite different from exposure occurring in adulthood.
That makes the detection of glyphosate in amniotic fluid particularly noteworthy.
The question isn’t simply whether a particular dose makes an adult animal visibly sick.
It is whether exposure during development can alter processes that are taking place at precisely the time those processes are establishing how the body will function later.
And increasingly, researchers are asking another question: could some of those effects extend into subsequent generations?
The 2025 mouse study raised it.
This new rat study raises it again.
What This Study Does — and Doesn’t — Tell Us
There are good reasons to be cautious about interpreting the findings.
This is one animal study. It cannot tell us what level of glyphosate exposure during human pregnancy would produce an effect, if any. It cannot establish that the developmental changes observed in rats will occur in people. And it does not explain exactly why some effects became more pronounced in the second generation.
Those are important limitations.
But the findings shouldn’t be dismissed simply because they don’t answer every question.
The researchers found glyphosate in amniotic fluid. They observed altered oxidative balance and developmental effects. They found intrauterine growth restriction in the second generation. They found greater vulnerability among male offspring. And they found that the commercial glyphosate-based herbicide generally produced more severe effects than glyphosate alone.
Those are findings that warrant further investigation.
Why These Findings Warrant Further Investigation
One animal study can raise a question.
When different studies begin raising similar questions, that is when the wider pattern becomes worth watching.
We now have separate studies in mice and rats reporting effects following glyphosate exposure during pregnancy that extended beyond the directly exposed generation.
They don’t prove that the same thing happens in humans.
But neither do we have the luxury of conducting controlled multigenerational experiments on pregnant women to find out.
That is precisely why developmental toxicology exists.
And when research suggests that exposure during pregnancy may reach the developing fetus — and that some biological effects may extend into the following generation — the appropriate response isn’t to pretend the unanswered questions don’t exist.
It is to investigate them.
Study
Almirón A, Lorenz V, Attademo AM, Demonte LD, Repetti MR, Durando M, Milesi MM. Multigenerational effects of perinatal glyphosate exposure in rats: Developmental alterations, increased mortality and oxidative imbalance.
Environmental Toxicology and Pharmacology. 2026;125:105065.
Read the study: https://doi.org/10.1016/j.etap.2026.105065
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