The Placenta’s Double Role: Shield and Gateway in Maternal-Fetal Health

For decades, the placenta has been seen as a life source between mother and child, providing blood supply and nutrition to the growing baby, as well as removing waste. It is often described as a shield, but in reality it is a porous gateway.

Alongside vital nutrients and oxygen, it can also absorb and transfer harmful substances from a mother’s body to her developing baby. These include toxic metals such as cadmium, pollutants like microplastics, and industrial chemicals known as endocrine-disrupting chemicals (EDCs).

History has shown how vulnerable fetal development is to outside influences. The thalidomide tragedy of the 1950s revealed that chemicals taken during pregnancy can cause devastating effects, from limb deformities to organ damage. Today, scientists know that many manufactured substances - including pesticides, plastics, and industrial by-products - can cross the placenta, affecting development in ways that may not become apparent until later in life.

These findings, while no doubt concerning to expecting mothers, should not be considered as a matter of individual responsibility alone though. This is a collective issue - and one that we cannot continue to ignore.

The Science: What the Placenta Can and Cannot Block

Microplastics and Nanoplastics

Over the past century, global plastic production has surged. In Europe alone, production reached approximately 413.8 million tons in 2023, up from 58 millions of tons in 2014, underscoring both the scale and the persistence of plastic dependence. By 2060, plastic waste is expected to triple to more than 1 billion tons - and, while it provides convenience for many, it also creates grave concern.

In 2021, researchers in Italy used Raman microspectroscopy to detect microplastics - particles smaller than five millimetres formed through the breakdown of plastic products - in human placentas for the first time.

The team analysed six placentas from healthy pregnancies and identified 12 fragments ranging from 5–10 μm in size. These were located across the fetal side, maternal side, and chorioamniotic membranes. Most were pigmented, including stained polypropylene - a common thermoplastic polymer - while others contained pigments typically used in industrial coatings, adhesives, cosmetics, and personal care products. This study demonstrated that plastics from everyday environments are capable of crossing into one of the body’s most critical interfaces between mother and child.

Building on this, a 2024 study published in Toxicological Sciences and led by Matthew Campen, PhD, at the University of New Mexico, analysed 62 human placentas and detected microplastics in every single case.

Concentrations ranged from 6.5 to 790 micrograms per gram of tissue, with polyethylene identified as the most common polymer. While the quantities may appear small, the authors cautioned that the steady rise of environmental microplastics raises significant concerns for long-term maternal and child health.

A pilot study in South China detected microplastics not only in placentas but also in cord blood and meconium, directly demonstrating fetal exposure. Exposure to microplastics has adverse effects on human health. The researchers note that participants with detectable microplastics in their arterial samples have a 4.53-fold increased risk of developing heart disease, stroke, and all-cause mortality, compared to those who do not.

Research has further shown that maternal exposure to micro- and nanoplastics during pregnancy can disrupt immune regulation between mother and foetus, alter placental metabolism, and impair overall placental function.

These exposures have also been linked to adverse outcomes in offspring, including abnormal brain development, metabolic disorders, and restricted growth. Taken together, the evidence underscores the critical importance of addressing maternal and foetal exposure to microplastics during pregnancy.

It is almost impossible to avoid exposure to microplastics though - with it being found in toothpaste, scrubs, masks, drinking water (tap and bottled), seafood, tea, honey, takeaways, and table salt - to name just a few locations.

Heavy Metals and Chemical Pollutants

The placenta can also absorb toxic metals. In the case of cadmium (Cd) exposure, the placenta plays a dual role: it accumulates the toxic metal while also allowing a portion to pass to the fetus.

Cadmium is taken into the body mainly through food such as cereals, seafood and organ meats, and through tobacco smoke (Järup & Åkesson, 2009). Once in the bloodstream it lingers for years, particularly in the kidneys, and has been linked to kidney and bone damage, increased cancer risk (Straif et al., 2009) and disruption of hormone function (Ali et al., 2010; Johnson et al., 2003).

Studies show that cadmium builds up in the placenta (Kippler et al., 2010; Osman et al., 2000). But the organ is no complete shield: levels in cord blood rise in step with maternal exposure (Kippler et al., 2010), meaning that what the mother absorbs, the fetus does too. This passage has been connected to poorer pregnancy outcomes.

Smaller studies have found links between high placental cadmium and reduced birth size (Galicia-Garcia et al., 1997; Nishijo et al., 2004; Zhang et al., 2004) or preterm delivery (Nishijo et al., 2002). The picture is complicated - two larger investigations found no such association (Odland et al., 1999; Osman et al., 2000) - but the overall weight of evidence suggests the placenta functions both as a storehouse and a conduit for cadmium.

One of the most revealing studies came from Bangladesh in 2010, where researchers found that women with higher cadmium in their placentas had babies with lower zinc in their cord blood (Kippler et al., 2010). That points to cadmium displacing essential nutrients, turning the placenta from a protective filter into a vulnerable interface – one where toxic metals can edge out the elements most critical for foetal growth.

Endocrine-Disrupting Chemicals

Another major concern is endocrine-disrupting chemicals, such as bisphenol A (BPA), widely used in plastics and resins entering the placenta. BPA has been measured by researchers not only in placental tissue, but also in amniotic fluid and cord blood - sometimes at concentrations higher than in the mother herself.

This shows how the placenta can actually concentrate harmful substances, rather than block them. Because hormones play a crucial role in pregnancy and brain development, even small amounts of these chemicals may interfere with growth, metabolism, or neurological development.

The growing brain of the foetus is especially vulnerable. While most of its structures form before birth, crucial processes such as rapid growth, myelination, and network formation continue into early childhood. Exposure to chemicals absorbed and passed on by the placenta - like BPA or other EDC - —has been linked in animal and human studies to growth restriction, learning difficulties, and an increased risk of neuro-developmental disorders.

A Myriad of Concern

It is rarely a single substance that poses the greatest risk. The placenta, and through it the foetus, is exposed to a complex mix of chemicals every day. Researchers now talk about the “neuroexposome”: the totality of environmental exposures - from plastics to pollutants to stress - that interact with genetics to shape long-term health. The placenta sits at the centre of this exchange, underscoring that pregnancy is not just a personal matter, but one that reflects the broader chemical environment we all live in.

Implications for Child Health

The absorption of pollutants in the placenta has measurable downstream impacts:

• Pre-term birth and low birth weight: A recent presentation at the Society for Maternal-Fetal Medicine (SMFM) reported that microplastics and nanoplastics were found in significantly higher concentrations in placentas from preterm births compared to term births. Researchers analysed 175 placentas (75 from preterm and 100 from full-term deliveries) and found the preterm placentas contained substantially more plastic - up to 203 μg/g tissue versus around 130 μg/g in term placentas

• Neuro-developmental outcomes: Prenatal exposure to lead and mercury is consistently correlated with lower IQ and attentional difficulties (Grandjean & Landrigan, Lancet Neurology, 2014).

• Respiratory and immune function: A 2017 systematic review in Environmental Research found statistically significant associations between prenatal exposure to air pollutants - specifically NO₂, SO₂, and PM₁₀ - and the development of childhood wheezing and asthma.

  
  

These outcomes carry economic consequences: increased healthcare costs, lower educational attainment, and reduced workforce productivity - making placental health a macroeconomic issue.

Rethinking Responsibility: Beyond the Mother

Focusing solely on maternal lifestyle overlooks the systemic drivers of exposure. A mother cannot prevent airborne microplastics in a polluted city, nor can she eliminate PFAS when they are present in water supplies and consumer packaging. Placing responsibility exclusively on mothers risks inequity, adding shame and fear into women already trying impossibly hard to protect their unborn baby, and ignores the root causes of exposure - to which millions of women simply cannot avoid.

This point is underscored by data from China, where industrial growth and urban air pollution mean pregnant women living there are among the most exposed globally. Other bio-monitoring work has shown higher levels of PFAS, heavy metals such as cadmium, and endocrine-disrupting chemicals in Chinese pregnant women compared to populations in Europe or North America. These findings reflect not individual behaviour, but systemic environmental conditions - industrial emissions, water contamination, and consumer goods regulation - that shape maternal and fetal health outcomes.

In such contexts, it is clear that maternal choices - diet, exercise, or use of prenatal supplements - cannot offset the scale of environmental exposures. Addressing these risks requires structural action: cleaner air, stricter chemical regulation, safer water infrastructure, and corporate responsibility for materials in global supply chains. The placenta, in this sense, becomes not just a biological organ, but a lens through which we can see how environmental policy, industrial practice, and public health intersect.

A Collective Agenda

• Governments and regulators must tighten emission controls and chemical safety standards (e.g., EU REACH framework).

• Healthcare systems should integrate biomonitoring of pollutants into prenatal care.

• Industry must innovate in safer materials and increase transparency about chemical exposure.

• Society at large should frame placental health as a public good - akin to clean water or vaccination - rather than a matter of individual choice.

  
  

A Call For Action

Research from Europe, Asia, and North America converges on a single conclusion: the placenta is not an impermeable barrier, but a permeable interface, absorbing and transferring pollutants with profound implications for fetal development. From toxic metals to microplastics and endocrine-disrupting chemicals, the evidence shows that the intrauterine environment is shaped as much by the air we breathe, the food we consume, and the materials we manufacture as by individual maternal choices.

Protecting the foetus, therefore, is inseparable from protecting maternal environments. Clean air, safe food systems, chemical regulation, and transparent supply chains are as critical to pregnancy outcomes as prenatal vitamins or clinical care.

The science underscores a simple truth: a healthy pregnancy cannot be achieved by mothers in isolation - it depends on the structures, policies, and practices of the societies in which they live.

Responsibility does not lie with the mother alone, but with all of us: governments that set regulatory standards, industries that design and release products, healthcare systems that monitor and educate, and communities that demand accountability.

Framing placental health as a collective responsibility is not just an ethical imperative but an economic one, given the long-term costs of compromised child health.

In short, safeguarding the placenta means safeguarding the next generation. The challenge is systemic, and so too must be the solutions.