# 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](https://support.elicit.com/en/articles/553025) across over 126 million academic papers from the [Semantic Scholar](https://www.semanticscholar.org/) 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.

- **Study Design**:
Describe the specific type of experimental design used in the study.

- **Participant Characteristics**:
Extract specific details about the study subjects.

- **Microplastic Characteristics**:
Capture detailed information about the microplastics used.

- **Primary Outcomes Measured**:
List all primary outcomes examined in the study related to pregnancy and microplastic exposure.

- **Key Findings**:
Summarize the most significant findings of the study.

## Results

### Characteristics of Included Studies

| Study | Study Design | Microplastic Type/Size | Exposure Route | Species/Model | Full text retrieved |
|-------|--------------|-------------------------|----------------|----------------|---------------------|
| Aghaei et al., 2022 | Animal experimental | Polystyrene, 5 μm and 50 nm | Drinking water | Mice | No |
| Amereh et al., 2022 | Observational cross-sectional | Polyethylene, Polystyrene, <5 mm | Not applicable (detected in placenta) | Human | No |
| Barrozo et al., 2024 | Observational | Polyethylene, < 20 μm | Not applicable (detected in placenta) | Human | No |
| Cary et al., 2024 | Animal experimental | Polystyrene nanoplastic | Intratracheal instillation | Rats | No |
| Chen et al., 2022 | Animal experimental | Polystyrene, 100 nm | Drinking water | Mice | No |
| Chen et al., 2024a | Animal experimental | Polystyrene, 6-154 μm | Oral gavage | C57BL/6J mice | Yes |
| Chen et al., 2024b | Animal experimental | Polystyrene, 50 nm | Oral gavage | Rats | No |
| Dibbon et al., 2023 | Animal experimental | Polystyrene, 5 µm and 50 nm | Drinking water | CD-1 mice | No |
| Dou et al., 2024 | Animal experimental | Polystyrene | Lactational exposure | Mice | No |
| Fournier et al., 2020 | Animal experimental | Polystyrene, 20 nm | Intratracheal instillation | Sprague Dawley rats | Yes |

### Effects of Microplastic Exposure

#### Maternal Effects

##### Observed Changes

| Study | Effect Category | Observed Changes | Exposure Level | Significance |
|-------|----------------|------------------|----------------|--------------|
| Aghaei et al., 2022 | No mention found | No mention found | 102, 104, or 106 ng/L | No mention found |
| Amereh et al., 2022 | Not applicable (observational) | No mention found | Not applicable | No mention found |
| Barrozo et al., 2024 | Not applicable (observational) | No mention found | Not applicable | No mention found |
| Cary et al., 2024 | Cardiovascular | Increased heart weight, vascular dysfunction in aorta and uterine artery | No mention found | No mention found |
| Chen et al., 2022 | No mention found | No mention found | 1 and 10 mg/L | No mention found |

#### Placental and Fetal Effects

##### Observed Changes

| Study | System Affected | Observed Changes | Exposure Level | Key Findings |
|-------|----------------|------------------|----------------|--------------|
| Aghaei et al., 2022 | Fetal growth | 12% decrease in fetal weight | 106 ng/L | Significant fetal growth restriction at highest exposure |
| Amereh et al., 2022 | Fetal growth, Development | Reduced birth weight, length, head circumference, 1-min Apgar score | Not applicable (observational) | Inverse associations between microplastic exposure and birth outcomes |
| Barrozo et al., 2024 | Placenta | Microplastic accumulation | Mean 6.91 mg/g | Microplastics detected in 100% of placentae |
| Cary et al., 2024 | Fetal growth, Cardiovascular | Reduced fetal and placental weight, dysregulated fetal heart, aorta, and umbilical artery function | No mention found | Significant cardiovascular effects in fetuses |
| Chen et al., 2022 | Fetal growth, Metabolism | Reduced fetal weights, abnormal cell morphologies, metabolic disturbances | 10 mg/L | Significant fetal growth restriction and metabolic changes |

### 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 in offspring tissues.
- **Inflammation**: Increased levels of inflammatory markers in neonatal livers.
- **Metabolic Alterations**: Disturbances in cholesterol metabolism in the placenta.
- **Gene Expression Changes**: Upregulation of genes involved in lipid metabolism.
- **Neurotransmitter Alterations**: Reduced levels of neurotransmitters in offspring.

### 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**: Dose-dependent structural damage to the placenta.

### Route-Specific Effects
#### Oral Exposure Outcomes
- Fetal growth reduction associated with higher concentrations of polystyrene microplastics in drinking water.
- Altered umbilical artery blood flow in exposed mice.

#### Respiratory Exposure Outcomes
- Reduced fetal and placental weight after exposure to polystyrene nanoplastics.
- Increased oxidative stress and inflammation markers in neonatal livers.

## References
1. [Impact of Microplastics on Pregnancy and Fetal Development: A Systematic Review](/content/review/648e681a-4715-423b-be06-bfef11664d1a/source/12e2fb19c65c451895cc22bfd625df9c/index.html)
2. [Microplastics from disposable paper cups are enriched in the placenta and fetus...](/content/review/648e681a-4715-423b-be06-bfef11664d1a/source/511a39ba9879465f8ce620e438cde158/index.html)
3. [Toxicities Demonstrated in Dams and Neonates...](/content/review/648e681a-4715-423b-be06-bfef11664d1a/source/a294c29b6c204c3fbea42e4b574befda/index.html)