Effects of Microplastics on Pregnancy

What are the effects of microplastic exposure during pregnancy?

Research shows that maternal exposure to microplastics during pregnancy disrupts maternal physiology, compromises placental integrity, and impairs fetal growth and development.

Abstract

Microplastic exposure during pregnancy shows measurable impacts on maternal physiology, placental integrity, and fetal development. In rodent studies, exposure to primarily polystyrene and polyethylene particles via drinking water, oral gavage, or inhalation has been associated with the following outcomes:

1. Maternal changes such as altered cardiovascular parameters (e.g., increased heart and spleen weight, vascular dysfunction), reproductive delays (e.g., disturbed estrous cyclicity and diminished fertility), metabolic disruptions, and shifts in liver weight or function.
2. Placental findings that include accumulation of microplastics (with one report noting a mean concentration of 6.91 mg/g in 100% of placentae) and altered vascular flow—up to a 43% increase in umbilical artery flow in one study.
3. Fetal effects marked by growth restriction—for example, a 12% reduction in fetal weight at 106 ng/L exposure—and neurodevelopmental disruptions, including hippocampal ferroptosis, reduced myelin formation, and altered neurotransmitter levels.

Biochemical assessments reveal increased oxidative stress, inflammation, and modulated gene expression linked to lipid metabolism and angiogenesis. In several experiments, higher doses (for instance, exposures equivalent to levels producing dose-dependent effects in mice) correspond with more pronounced adverse outcomes. These findings indicate that microplastic exposure during gestation may perturb maternal, placental, and fetal systems in measurable ways.

Methods

We analyzed 40 sources from an initial pool of 499, using 5 screening criteria. Each paper was reviewed for 5 key aspects that mattered most to the research question. More on methods

Papers identified with Elicit search

n = 499

Papers screened using: Study Population, Exposure Assessment, Outcome Measures, Study Design, Exposure Quantification

n = 499

Papers screened out

n = 459

Papers included for extraction

n = 40

Paper search

Using your research question “What are the effects of microplastic exposure during pregnancy?”, we searched across over 126 million academic papers from the Semantic Scholar corpus. We retrieved the 499 papers most relevant to the query.

Screening

We screened in sources based on their abstracts that met these criteria:

• Study Population: Does the study include pregnant humans or animals AND report clear pregnancy-related outcomes?
• Exposure Assessment: Does the study examine microplastic (not macroplastic) exposure through any route (ingestion, inhalation, or dermal) using clear assessment methodology?
• Outcome Measures: Does the study measure specific maternal, fetal, or pregnancy outcomes during any stage of pregnancy?
• Study Design: Is the study either a primary research study (experimental or observational) or systematic review with a sample size of at least 10?
• Exposure Quantification: Does the study include biological measurements or outcomes related to microplastic exposure (not just environmental concentrations)?

We considered all screening questions together and made a holistic judgement about whether to screen in each paper.

Data extraction

We asked a large language model to extract each data column below from each paper. We gave the model the extraction instructions shown below for each column.

• Study Design:

Describe the specific type of experimental design used in the study. Look in the Methods section for details such as:

• Type of study (e.g., animal experimental study, in vivo experiment)

• Specific model used (e.g., pregnant mice, pregnant rats)

• Experimental groups (number and type) If multiple design elements are present, list all relevant details. If unclear, note “design not clearly specified”.

• Participant Characteristics:

Extract specific details about the study subjects:

• Species used (e.g., ICR mice, rats)

• Strain or type of animal

• Pregnancy stage or gestational age at start of experiment

• Number of animals per group

• Age of animals (if reported)

• Sex (though likely all female for pregnancy studies) Be as precise as possible. If any characteristic is not reported, write “Not reported”.

• Microplastic Characteristics:

Capture detailed information about the microplastics used:

• Type of microplastic (e.g., polyethylene, polystyrene)

• Particle size (in μm or mm)

• Concentration of exposure (include units)

• Method of administration (e.g., intragastric intubation, pulmonary exposure)

• Duration of exposure If multiple characteristics are reported, list all details comprehensively.

• Primary Outcomes Measured:

List all primary outcomes examined in the study related to pregnancy and microplastic exposure:

• Maternal outcomes (e.g., body weight, glucose homeostasis, organ function)

• Fetal/offspring outcomes (e.g., birth weight, organ weight, developmental markers)

• Biochemical markers (e.g., acetylcholinesterase, glutathione peroxidase) Include specific measurements and units if provided. Prioritize outcomes directly related to pregnancy effects.

• Key Findings:

Summarize the most significant findings of the study:

• Statistically significant changes in maternal or fetal outcomes
• Observed biological mechanisms
• Dose-dependent effects
• Potential implications for pregnancy health Focus on results directly addressing microplastic exposure effects. Quote exact numerical results or statistical significance if available.

Results

Characteristics of Included Studies

The extracted data indicates that many of the included studies were animal experiments, often using mice models, and frequently examining polystyrene nano- and microplastics. The diversity in exposure routes reflects the complex nature of microplastic exposure in biological systems.

• Study Design:

  • Animal experimental: 33 studies
  • Observational: 6 studies
  • In vitro: 2 studies
  • Systematic review: 1 study

• Microplastic Type:

  • Polystyrene: 28 studies
  • Polyethylene: 8 studies
  • Various or not specified: 4 studies

• Microplastic Size:

  • Nanoplastics: 19 studies
  • Microplastics: 15 studies
  • No size information found: 8 studies

• Exposure Route:

  • Drinking water: 5 studies
  • Detection in placenta: 5 studies
  • Oral gavage: 4 studies
  • Intratracheal instillation: 3 studies
  • Maternal transfer: 2 studies
  • No exposure route information found: 7 studies

• Species/Model:

  • Mice: 25 studies
  • Rats: 8 studies
  • Human: 7 studies
  • Other (e.g., chick embryos, cell lines): 2 studies

Effects of Microplastic Exposure

Maternal Effects

The studies reported various maternal effects associated with microplastic exposure during pregnancy:

• Effect Categories:
  • Body weight: 3 studies
  • Reproductive: 2 studies
  • Metabolic: 2 studies
  • Hepatic: 2 studies
  • Other categories (Cardiovascular, Mammary gland development, Organ deposition, Organ weight, Uterine changes, Immune system, and Liver weight): 1 study each
  • No effect categories found: 21 studies
  • Not applicable (observational studies): 6 studies
• Observed Changes: 13 out of 40 studies reported specific observed changes. These changes varied widely, including effects on body weight, reproductive system, metabolism, liver function, cardiovascular system, and immune system.
• Exposure Levels: 22 out of 40 studies reported exposure levels. The exposure levels varied greatly in both units and magnitudes, ranging from ng/L to mg/kg/day.
• Statistical Significance: Only 1 out of 40 studies reported statistical significance of the results.

Placental and Fetal Effects

The included studies reported a variety of effects associated with microplastic exposure during pregnancy and early postnatal development, potentially affecting multiple organ systems and developmental processes:

• Most Frequently Studied Systems:

  • Fetal growth: 16 studies
  • Placenta: 10 studies
  • Neurodevelopment: 7 studies
  • Hepatic system: 5 studies

• Most Commonly Observed Changes:

  • Fetal weight decrease or reduced birth weight: 11 studies
  • Neurodevelopmental effects: 7 studies
  • Fetal growth restriction or effects: 6 studies
  • Microplastic presence or accumulation: 4 studies
  • Placental dysfunction or damage: 4 studies

• Key Findings Across Studies:

  • Fetal growth effects or restriction: 13 studies
  • Neurodevelopmental effects: 7 studies
  • Placental effects: 6 studies
  • Microplastics detected in placenta or meconium: 4 studies
  • Hepatic effects: 3 studies

Multiple studies reported significant effects on fetal growth, neurodevelopment, and placental function. Several studies also detected microplastics in placental tissue and meconium. Additionally, we found reports of metabolic changes, reproductive effects, and multi-system impacts in offspring exposed to microplastics during development.

Biochemical and Molecular Changes

The studies reported a range of biochemical and molecular changes associated with microplastic exposure during pregnancy:

• Oxidative Stress:
  • Increased malondialdehyde generation and altered superoxide dismutase and catalase activities in offspring tissues.
  • Increased oxidative stress in lung tissues of offspring.
• Inflammation:
  • Increased levels of inflammatory markers such as monocyte chemoattractant protein-1 and tumor necrosis factor-alpha in neonatal livers.
  • Increased levels of IL-1β, IL-6, and TNF-α in fetal brain regions.
• Metabolic Alterations:
  • Disturbances in cholesterol metabolism and complement and coagulation cascades pathways in the placenta.
  • Alterations in serum metabolites, including amino acids and acyl-carnitines, indicating potential fatty acid metabolism disorders.
• Gene Expression Changes:
  • Upregulation of genes involved in de novo lipogenesis, fatty acids uptake, and triacylglycerol synthesis in maternal and offspring livers.
  • Dysregulation of genes involved in angiogenesis and visual system development in the retina.
• Hormonal Changes:
  • Elevated testosterone levels in female mice exposed to microplastics.
• Neurotransmitter Alterations:
  • Reduced γ-aminobutyric acid (GABA) levels in the prefrontal cortex and amygdala of offspring.
  • Alterations in monoamine and amino acid neurotransmitters in the cortex and hippocampus.
• Cellular Apoptosis:
  • Increased apoptosis in placental tissues, associated with activation of the Bcl-2/Cleaved-caspase-2/Cleaved-caspase-3 signaling pathway.
• Epigenetic Changes:
  • Changes in pathways related to DNA methylation and histone modification in offspring.

Dose-Dependent Relationships

Several studies reported dose-dependent effects of microplastic exposure during pregnancy:

• Fetal Growth:
  • Observed dose-responsive harmful effects on fetal development, with moderate intake significantly altering cecal microbiome composition and metabolic functions.
  • A 12% decrease in fetal weight at the highest exposure concentration.
• Placental Effects:
  • Maternal exposure to polystyrene nanoplastics caused dose-dependent structural damage to the placenta.
• Neurodevelopmental Effects:
  • Observed that smaller particle sizes and higher doses had more significant neurotoxic effects on fetal development.
• Reproductive Toxicity:
  • Exposure to polystyrene nanoplastics at high doses induced miscarriage in a dose-dependent manner.

Route-Specific Effects

Oral Exposure Outcomes

Oral exposure to microplastics during pregnancy, typically through drinking water or gavage, was a common route of administration in many of the included studies.

• Fetal Growth:
  • Significant declines in fetal weights at higher concentrations (10 mg/L) of polystyrene nanoplastics in drinking water.
• Placental Effects:
  • Reported altered umbilical artery blood flow and placental dysfunction in mice.
• Metabolic Effects:
  • Found that oral exposure led to metabolic disorders, associated with gut microbiota dysbiosis and gut barrier dysfunction.

Respiratory Exposure Outcomes

Several studies examined the effects of respiratory exposure to microplastics during pregnancy:

• Fetal Growth and Development:
  • Reduced fetal and placental weight observed following pulmonary exposure to polystyrene nanoplastic.

References

• R. K. Sharma, Usha Kumari, Sudhir Kumar (2024). Impact of Microplastics on Pregnancy and Fetal Development: A Systematic Review. Cureus
• Qiong Chen, Chen Peng, Haoteng Xu, Zhuojie Su, Gulimire Yilihan, and 3 more (2024). Microplastics from disposable paper cups are enriched in the placenta and fetus, leading to metabolic and reproductive toxicity during pregnancy. bioRxiv
• Youngmi Song, Changyul Kim (2021). Toxicities Demonstrated in Dams and Neonates following Intragastric Intubation of Polyethylene Microplastics to Pregnant Mice. Journal of Environmental Health Sciences
• Zahra Aghaei, J. Sled, J. Kingdom, A. Baschat, P. Helm, and 2 more (2022). Maternal Exposure to Polystyrene Micro- and Nanoplastics Causes Fetal Growth Restriction in Mice. Environmental Science & Technology Letters