Microplastics in Preterm Placentas, Higher Than Blood Levels
The placenta sits at the boundary between a pregnant person and the outside world. It transfers nutrients, filters substances, and regulates immune signals. A study published in early 2025 found that this tissue accumulates microplastics and nanoplastics at concentrations higher than those previously measured in human blood, and that preterm placentas accumulate even more than those from full-term pregnancies.
Where Microplastics Come From
Plastic does not disappear. It breaks down into progressively smaller fragments, eventually reaching microscopic scale.
Particles smaller than 5mm are classified as microplastics. Those smaller than 1 micrometer (one millionth of a meter) are nanoplastics. These particles enter the body through five main routes.
Food and water: Plastic bottled water consistently contains more microplastic particles than filtered tap water or water from glass containers. Disposable packaging, plastic cups, and containers heated in the microwave shed particles into food. Some estimates suggest the average person ingests around 5 grams of microplastics per week, roughly the weight of a credit card.
Inhalation: Synthetic fabrics such as polyester, nylon, and acrylic shed microfibers during washing. Those fibers circulate through dryers and ventilation systems into indoor air. Urban outdoor air and household dust both contain measurable concentrations of airborne microplastics.
Skin contact: Long-term contact with synthetic textiles and certain cosmetic scrub formulations represent possible routes. Data on transdermal absorption remains limited, but research is ongoing.
Cooking and heating: Heat accelerates particle release from plastic containers. Microwaving food in plastic, pouring boiling water into plastic kettles, or using plastic utensils in hot food all contribute.
Environmental accumulation: Microplastics have been found in soil, seafood, and vegetables throughout food systems globally. The distribution is broad enough that no single source explains the full exposure picture.
175 Placentas, Two Groups
The study was led by Dr. Enrico R. Barrozo at Baylor College of Medicine, with Dr. Kjersti Aagaard of Boston Children’s Hospital as senior author, in collaboration with the University of New Mexico.
Researchers analyzed 175 placentas using high-sensitivity mass spectrometry: 100 from full-term births (37 weeks or later) and 75 from preterm births (before 37 weeks). The findings were presented January 30, 2025 at SMFM’s annual meeting and published in the journal Pregnancy.
Preterm placentas showed significantly higher concentrations of both microplastics and nanoplastics compared to term placentas. What made this particularly striking was the timeline. Preterm infants spent less time in the womb, yet their placentas contained more plastic. As Barrozo noted, the preterm group “accumulated more, but did so at an earlier time point in pregnancy,” suggesting accelerated accumulation rather than simple proportional buildup over time.
Higher Than Blood, Inside the Placenta
The concentration of microplastics and nanoplastics in the placentas exceeded levels previously measured in human blood. This matters because blood represents the body’s most widely distributed transport medium. A substance found at higher concentration in placental tissue than in blood suggests the placenta may be selectively concentrating these particles rather than simply reflecting what circulates in the bloodstream.
The placenta is designed to be selectively permeable. It decides what passes to the fetus and what does not. Nanoplastics, being extremely small, may be able to cross this barrier. Whether they do in meaningful quantities, and what consequences follow, are questions the current study does not answer. What it does establish is that the concentration gradient moves toward the placenta, not away from it.
Aagaard described the findings as hinting at the possibility that accumulated plastics “could be contributing to the risk and occurrence of preterm birth.” Not confirmed, not ruled out, but a plausible pathway that now has supporting data behind it.
Daily Exposure Routes
The findings refocus attention on where plastics actually enter the body in daily life.
Bottled water is one of the most studied sources. The physical process of manufacturing plastic bottles, opening and closing caps, and storing water in plastic all contribute particles. Studies comparing bottled water to filtered tap water in glass containers consistently show much higher particle counts in the plastic-packaged option.
Heated food containers are a significant and often overlooked source. Microwaving food in plastic containers, whether labeled “microwave-safe” or not, increases particle release. The label refers to structural integrity at heat, not the absence of particle migration. Transferring food to ceramic or glass before reheating removes this variable.
Synthetic clothing sheds during washing. A single polyester garment can release hundreds of thousands of microfibers per wash cycle. These fibers exit through drain water and also become airborne during the drying process, circulating through indoor air.
What You Can Actually Change
The gap between “exposure exists” and “here is what to do about it” is where practical guidance matters.
Switching from plastic water bottles to glass or stainless steel containers addresses one of the more quantifiable daily sources. The transition does not require eliminating all plastic from a household, just changing what holds your drinking water.
Keeping plastic and heat separate is a concrete adjustment that reduces kitchen exposure. Ceramic, glass, or cast iron for cooking and reheating. Avoiding polystyrene and single-use plastic cups for hot beverages. Moving hot food out of delivery packaging before eating.
Using a laundry mesh bag for synthetic fabrics does not eliminate microfiber release, but it reduces the amount that reaches indoor air and surface dust. Combined with regular ventilation and air filtration, this helps lower the indoor concentration a person breathes over time.
None of these changes come with a quantified risk reduction for preterm birth specifically. That data does not yet exist. What they represent is a way to reduce a measurable exposure, in a context where that exposure has been found at elevated levels in a tissue associated with pregnancy outcomes.
A Variable Reproductive Health Wasn’t Tracking Before
This study focused on placentas, but the implications extend to anyone thinking about reproductive health before pregnancy as well.
The placenta forms after implantation. What happens in the lead-up, during the egg and early embryo stages, when microplastics and related chemical compounds are already circulating, is a separate area of inquiry. Some researchers are investigating whether microplastics carry endocrine-disrupting chemicals that interact with hormonal signaling relevant to reproductive function. Clinical conclusions have not been established.
What the SMFM findings introduce is a new variable in the conversation about environmental health and fertility. It is not a conclusive answer, but it is evidence that the question is worth taking seriously.
Ongoing Research
The EU AURORA Project (2021-2026) is a multi-country study tracking environmental exposures during pregnancy across European cohorts. Microplastics and nanoplastics are among the primary variables being monitored. When its final data emerges, it will provide a much larger and longer-term picture than any single-site study can offer.
The Barrozo-Aagaard team is continuing to investigate how placental microplastic accumulation relates to fetal development, immune function, and post-birth health outcomes. The NIH, NSF, and NIEHS funded the current research, signaling institutional recognition that this line of inquiry warrants sustained attention.
The 2025 SMFM study established something specific: in placental tissue, plastic concentrations exceed blood levels, and preterm placentas concentrate more than term ones. The mechanism behind that gradient, and what it means for the pregnancies that produce it, is what the next round of research is now trying to answer.
Q. Does this study prove microplastics cause preterm birth?
No. This is an observational study showing correlation, not causation. It found higher microplastic concentrations in preterm placentas compared to term placentas, but a direct causal link has not been established. Senior author Dr. Kjersti Aagaard described the findings as “hinting at the possibility” that plastic accumulation “could be contributing to the risk and occurrence of preterm birth.” Ongoing studies including the EU AURORA project are expected to clarify this relationship.
Q. Can I eliminate microplastic exposure during pregnancy?
Complete elimination is not realistic given how widely microplastics are distributed across food, water, air, and clothing. The practical approach is to reduce exposure where possible: switching from plastic water bottles to glass or stainless steel containers, avoiding heating food in plastic containers, and using a laundry bag when washing synthetic fabrics. These changes can meaningfully lower your daily intake without requiring unrealistic lifestyle overhauls.
Q. Do microplastics in the placenta stay in the body after birth?
The placenta is delivered after birth, so microplastics concentrated there leave the body with it. What remains less understood is whether and how placental plastics affect fetal development during pregnancy, and whether nanoparticles small enough to cross the placental barrier reach the fetus. These are active areas of research. No medical procedure currently exists to remove microplastics from the placenta.