According to Gram Research analysis, perinatal exposure to polystyrene microplastics caused lasting changes in developing rats, including altered hormone levels, abnormal cholesterol, and sex-specific behavioral problems that persisted into adulthood. Male offspring showed increased anxiety and changed eating habits, while females ate more overall. This 2026 study of 17 rats suggests microplastics may disrupt normal development during critical windows, though human effects remain unknown.
Scientists discovered that when pregnant rats were exposed to microplastics—tiny pieces of plastic smaller than a grain of sand—both the mothers and their babies showed health problems. The babies had changes in their hormones, cholesterol levels, and behavior that lasted into adulthood. Male offspring became more anxious and ate differently, while females ate more overall. This research matters because microplastics are found everywhere in our environment, including in human breast milk and placentas, raising concerns about how they might affect human development and health.
Key Statistics
A 2026 animal study published in Food and Chemical Toxicology found that pregnant rats exposed to polystyrene microplastics gave birth to offspring with lasting changes in stress hormones, cholesterol, and thyroid function that persisted from weaning through adulthood.
In the same 2026 study of 17 rats, male offspring exposed to microplastics during pregnancy and nursing showed increased anxiety-like behavior during puberty and adulthood, plus reduced overall caloric intake but preference for high-fat foods.
According to the 2026 research, female offspring exposed to perinatal microplastics exhibited increased caloric intake in adulthood, while their mothers showed lower cholesterol and thyroid hormone levels at the time of weaning.
The 2026 study demonstrated that a single dose of 10-micrometer polystyrene microplastics during pregnancy caused sex-dependent behavioral and hormonal disturbances in offspring that lasted from puberty into adulthood.
The Quick Take
- What they studied: Whether exposure to microplastics during pregnancy and nursing causes problems in mothers and their developing babies
- Who participated: Pregnant Wistar rats (a common lab rat breed) were divided into two groups: 9 mothers received regular water, and 8 mothers received water with tiny plastic particles. Their babies were tracked from birth through adulthood
- Key finding: Babies exposed to microplastics showed lasting changes in hormones, cholesterol, and behavior into adulthood, with different effects in males versus females. Male offspring became more anxious and changed their eating habits, while females ate more
- What it means for you: This research suggests microplastics may affect how bodies develop and function, though this was a rat study and more research is needed to understand effects in humans. It highlights why reducing plastic pollution matters for health
The Research Details
Researchers gave pregnant rats either plain water or water containing tiny plastic particles (10 micrometers in size) starting from day 7 of pregnancy through weaning. They measured the mothers’ and babies’ body weight, hormone levels, cholesterol, and behavior at three key life stages: weaning (3 weeks old), puberty (6.5 weeks old), and adulthood (4 months old). Behavioral tests included observing how anxious the rats were and what foods they preferred.
This design allowed scientists to see if microplastic exposure during critical development periods caused problems that lasted into adulthood. By measuring at multiple time points, they could track whether changes happened early or developed over time. The researchers also compared males and females separately to see if microplastics affected them differently.
This approach is important because it mimics how human babies are exposed to microplastics—through their mothers during pregnancy and breast milk after birth. By following the animals from birth to adulthood, researchers could see if early exposure causes lasting damage. Testing behavior alongside hormones and cholesterol helps explain how microplastics might affect the brain and body systems that control growth, mood, and eating
This was a controlled laboratory study where researchers could carefully measure exposure and track outcomes. The sample size was relatively small (17 rats total), which is typical for animal studies but means results should be confirmed in larger studies. The study used established behavioral tests and measured multiple body systems, making the findings more reliable. However, rats are not humans, so we cannot assume the same effects occur in people without further research
What the Results Show
Mothers exposed to microplastics weighed less during pregnancy but returned to normal weight while nursing. However, they had lower cholesterol and thyroid hormone (T4) levels when their babies were weaned.
The babies showed the most dramatic changes. At different life stages, they had abnormal levels of cholesterol, triglycerides (another type of fat), and hormones including corticosterone (a stress hormone), thyroid hormones, leptin (which controls hunger), and FSH (which controls reproduction). These changes appeared at different ages in different offspring, suggesting microplastics affect development in complex ways.
Behavior changes were particularly striking and sex-specific. Male offspring became noticeably more anxious during puberty and stayed anxious into adulthood. They also ate fewer calories overall but preferred high-fat foods. Female offspring showed the opposite pattern—they ate more calories as adults. These behavioral changes suggest microplastics may affect brain regions controlling anxiety and appetite differently in males versus females.
The study found that effects varied depending on the offspring’s age and sex, indicating that microplastics don’t cause one simple problem but rather multiple interconnected changes. The fact that some changes appeared at puberty and others in adulthood suggests microplastics may disrupt normal development at critical windows. The sex-specific differences are particularly important because they suggest microplastics may interfere with hormones that differ between males and females
This research builds on growing evidence that microplastics can disrupt endocrine (hormone) systems and affect behavior. Previous studies showed microplastics in human tissues including placentas and breast milk, but few studies examined effects during critical developmental windows. This work is among the first to systematically track how perinatal (around birth) microplastic exposure affects multiple body systems from infancy through adulthood, making it a significant contribution to understanding potential human health risks
The study used rats, not humans, so we cannot directly apply these findings to people. The sample size was small (17 rats), which limits how confident we can be in the results. The study used only one type of microplastic (polystyrene) at one dose, so we don’t know if other plastics or different amounts would cause similar problems. The study didn’t measure microplastics in the rats’ tissues, so we don’t know exactly how much plastic accumulated in their bodies. Finally, this was a single study, so results need confirmation by other research groups before drawing firm conclusions
The Bottom Line
Based on this research, reducing exposure to microplastics during pregnancy and nursing appears important for protecting developing babies. While this is animal research, the findings suggest pregnant people should minimize plastic use where possible—choosing glass or metal containers, avoiding single-use plastics, and being aware that microplastics are in many foods and water sources. However, these are precautionary recommendations based on animal evidence, not yet proven in humans. Confidence level: Moderate (animal evidence is strong, but human studies are limited)
Pregnant people and those planning pregnancy should be most concerned, as the study showed effects during critical development periods. Parents of young children may also want to reduce household plastic exposure. Public health officials should consider this evidence when developing policies about plastic pollution. The general public should know about this research as motivation to reduce plastic consumption, though individual risk cannot yet be quantified
In this rat study, some changes appeared within weeks (at weaning and puberty), while others developed over months into adulthood. If similar effects occur in humans, changes might appear during childhood development or puberty, though this is speculative. Long-term health effects in humans would take years or decades to observe
Frequently Asked Questions
Can microplastics affect a baby’s development during pregnancy?
According to a 2026 animal study, exposure to microplastics during pregnancy and nursing caused lasting changes in offspring’s hormones, cholesterol, and behavior into adulthood. Microplastics have been detected in human placentas and breast milk, raising concerns about similar effects in humans, though research is still limited.
Do microplastics affect boys and girls differently?
Yes, according to the 2026 research, males and females showed different responses. Male offspring became more anxious and ate less overall but preferred fatty foods, while females ate more calories as adults. This suggests microplastics may disrupt sex-specific hormones differently.
What are microplastics and where do they come from?
Microplastics are tiny plastic particles smaller than a grain of sand, created when larger plastics break down or shed from products. They’re found in ocean water, soil, air, food, and drinking water. They’ve been detected in human tissues including placentas and breast milk, indicating widespread environmental contamination.
How can I reduce microplastic exposure during pregnancy?
Use glass or metal containers instead of plastic for food and water storage, avoid single-use plastics, choose fresh foods over heavily packaged options, and filter drinking water. While this 2026 animal study suggests reducing exposure is prudent, individual human risk from microplastics hasn’t been precisely quantified yet.
Are the results from rats applicable to humans?
Animal studies provide important early evidence but cannot directly prove human effects. This rat research is significant because it shows microplastics can disrupt multiple body systems during development, but human studies are needed to confirm similar effects occur in people and at what exposure levels.
Want to Apply This Research?
- Track plastic consumption sources weekly: count single-use plastics used, water bottles consumed, and packaged foods eaten. Rate anxiety or mood changes on a 1-10 scale daily to establish baseline patterns
- Replace three single-use plastic items per week with reusable alternatives (water bottle, food containers, shopping bags). For pregnant users or those planning pregnancy, set a goal to eliminate single-use plastics from food storage within one month
- Monthly check-ins on plastic reduction progress and mood/anxiety patterns. For pregnant users, track alongside prenatal appointments. Create a household plastic audit quarterly to identify new reduction opportunities
This research was conducted in rats and does not directly prove effects in humans. Microplastic exposure in humans is complex and involves many variables not captured in animal studies. Pregnant people concerned about microplastic exposure should discuss individual risk factors with their healthcare provider. This article summarizes research findings and should not be considered medical advice. Always consult qualified healthcare professionals for personalized guidance about pregnancy health and environmental exposures.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.