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.

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.

Effects of Microplastic Exposure

Maternal Effects:

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

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. The findings suggest significant effects on fetal growth, neurodevelopment, and placental function.

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.
• Inflammation: Increased levels of inflammatory markers such as monocyte chemoattractant protein-1 and tumor necrosis factor-alpha.
• Metabolic Alterations: Disturbances in cholesterol metabolism and alterations in serum metabolites, indicating potential fatty acid metabolism disorders.
• Gene Expression Changes: 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 neurotransmitter levels in the prefrontal cortex and amygdala of offspring.
• Cellular Apoptosis: Increased apoptosis in placental tissues.
• Epigenetic Changes: Alterations in pathways related to DNA methylation and histone modification in offspring.

These biochemical and molecular changes varied depending on the type and size of microplastics, exposure route, and the particular organ system affected.

Dose-Dependent Relationships

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

• Fetal Growth: Dose-responsive harmful effects on fetal development.
• Placental Effects: Maternal exposure to polystyrene nanoplastics caused dose-dependent structural damage to the placenta.
• Hepatic Effects: Dose-dependent effects on liver weight, oxidative stress, and inflammation in offspring.
• Neurodevelopmental Effects: Smaller particle sizes and higher doses had more significant neurotoxic effects.
• Reproductive Toxicity: Certain doses induced miscarriage in a dose-dependent manner.
• Microplastic Accumulation: Observed a dose-dependent accumulation in neonate organs.

The presence of dose-dependent effects suggests that there may be threshold levels of exposure below which effects are minimal or undetectable. Chen et al. (2024a) suggests a benchmark dose of 2 to 4 cups/day during pregnancy based on their mouse model, although caution is advised in extrapolating such limits to humans.

Route-Specific Effects

Oral Exposure Outcomes

Oral exposure to microplastics was a common route of administration in many included studies. The outcomes associated with oral exposure were diverse and affected multiple systems:

• Fetal Growth: Significant declines in fetal weights at higher concentrations of polystyrene nanoplastics in drinking water.
• Placental Effects: Altered umbilical artery blood flow and placental dysfunction.
• Metabolic Effects: Leading to metabolic disorders and gut barrier dysfunction.
• Neurodevelopmental Effects: Caused ferroptosis in the hippocampus of offspring.
• Transgenerational Effects: Led to impaired reproductive outcomes in offspring.

Respiratory Exposure Outcomes

Several studies examined respiratory exposure to microplastics during pregnancy.

• Fetal Growth and Development: Significant effects on fetal and placental weight.
• Cardiovascular Effects: Increased heart weight and vascular dysfunction.
• Placental Translocation: Nanoplastics could cross the placental barrier and be detected in fetal tissues.

These findings highlight that respiratory exposure during pregnancy can have significant and wide-ranging effects.

References

1. R. K. Sharma, Usha Kumari, Sudhir Kumar (2024). Impact of Microplastics on Pregnancy and Fetal Development: A Systematic Review. Cureus
2. Qiong Chen, Chen Peng, et al. (2024). Microplastics from disposable paper cups are enriched in the placenta and fetus, leading to metabolic and reproductive toxicity during pregnancy. bioRxiv
3. 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
4. Zahra Aghaei et al. (2022). Maternal Exposure to Polystyrene Micro- and Nanoplastics Causes Fetal Growth Restriction in Mice. Environmental Science & Technology Letters
5. Katherine Dibbon et al. (2023). Polystyrene micro- and nanoplastics cause placental dysfunction in mice. Biology of Reproduction
6. Ruiying Zhang et al. (2024). Polystyrene microplastics disturb maternal glucose homeostasis and induce adverse pregnancy outcomes. Ecotoxicology and Environmental Safety
7. Lei Tian et al. (2024). Effects of nanoplastic exposure during pregnancy and lactation on neurodevelopment of rat offspring. Journal of Hazardous Materials
8. C. M. Cary et al. (2024). Single pulmonary nanopolystyrene exposure in late-stage pregnancy dysregulates maternal and fetal cardiovascular function. Toxicological Sciences.