Pregnant woman protected from air pollution by a bubble.

Is Air Pollution During Pregnancy Harming Your Baby? New Study Reveals a Hidden Risk

Jordan Keane monogram
Jordan Keane in Health & Wellness October 2026 • 5 min read.

"Household air pollution, often overlooked, may pose a significant threat to placental health and fetal development, according to recent research."


For many expecting mothers, concerns about diet, exercise, and prenatal care top the list of priorities. Yet, a less obvious but equally critical factor is increasingly coming to light: the impact of air pollution, specifically from household sources, on pregnancy and fetal development. While the dangers of urban smog and industrial emissions are widely recognized, the risks associated with indoor air quality, particularly in homes relying on biomass fuels, are often underestimated.

Millions worldwide still depend on solid biomass fuels like wood, charcoal, and crop residues for cooking and heating. This reliance releases a complex cocktail of pollutants, including fine particulate matter (PM2.5) and carbon monoxide (CO), directly into the living environment. Exposure to these pollutants during pregnancy has been linked to adverse outcomes such as low birth weight, stillbirth, and preterm birth. However, the underlying mechanisms through which these pollutants affect the developing fetus have remained unclear—until now.

A recent study conducted in Dar es Salaam, Tanzania, has provided critical insights into this area. Researchers investigated the association between household air pollution and placental pathology in pregnant women who primarily cook with charcoal. The findings reveal a potential link between exposure to PM2.5 and CO and fetal thrombotic vasculopathy (FTV), a condition affecting blood vessels in the placenta. This discovery highlights the importance of understanding and mitigating the risks of household air pollution to safeguard pregnancy health.

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Measuring Fetal Growth

Ultrasound is the gold standard approach for measuring fetal growth during pregnancy. Existing research has used ultrasound to examine how early-life air-pollution exposure may affect fetal growth, with most studies focusing on ambient air pollution. Researchers also use biomarkers to measure individual exposure to specific pollutants and investigate biological pathways linked to adverse outcomes. Prenatal risk factors, including sociodemographic, behavioral, physical-activity, and clinical factors, must also be considered when assessing birth outcomes.

A Developing Field

Research on air pollution and pregnancy has developed alongside broader efforts to understand air-quality risks and protect public health. The US EPA presents selected air-quality research milestones under the Clean Air Act in an historical timeline. A 2018 systematic review examined links among prenatal air-pollution exposure, placental omics markers, and possible disease development later in life. That review found six studies addressing this three-part relationship, while reporting that no metabolomic or exposomic data connecting the placenta with prenatal air-pollution exposure had yet been published.

Unveiling the Connection: How Household Air Pollution Impacts Placental Health

Pregnant woman protected from air pollution by a bubble.

The study, published in Environmental Health Perspectives, involved 116 pregnant women in urban and peri-urban Dar es Salaam. Researchers meticulously measured personal exposures to PM2.5 and CO over 72-hour periods and collected placentas after delivery for detailed examination. What made this study particularly strong was that the placental examinations were conducted "blinded," meaning the pathologists had no knowledge of the women’s pollution exposure levels, reducing potential bias.

The results revealed that the women in the study experienced moderate levels of air pollution. The average PM2.5 exposure was 40.5 µg/m³, with a staggering 88.6% of measurements exceeding World Health Organization air quality guidelines. The average CO exposure was 2.21 ppm.

  • Fetal Thrombotic Vasculopathy (FTV): The most striking finding was the association between increased PM2.5 and CO exposures and FTV. For each unit increase in exposure (on a logarithmic scale), the odds of FTV increased significantly.
  • FTV and Adverse Outcomes: FTV was more common in pregnancies complicated by stillbirth or low birth weight, underscoring the potential clinical significance of this placental pathology.
  • No Direct Link to Inflammation or Hypoxia: Contrary to initial hypotheses, the study did not find a statistically significant association between air pollution exposure and general inflammatory or hypoxic placental lesions.
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Current Evidence

The World Health Organization estimated that household air pollution caused 2.9 million deaths worldwide in 2021, including more than 309,000 deaths among children under five, and accounted for around 95 million disability-adjusted life years. Recent reviews describe environmental pollution and climate change as contemporary threats affecting gestation, fetal development, and postnatal health. A review of household air pollution likewise characterizes it as a continuing public-health challenge with implications for pregnant women and fetal well-being. That review associates exposure with low birth weight, neonatal mortality, and increased risks of hypertension and pneumonia.

Limits of the Evidence

A 2025 review reports that pregnant women are exposed to multiple air pollutants, including particulate matter. Its focus on long-term exposure emphasizes that maternal and child-health risks may arise from sustained environmental conditions rather than from a single pollutant or isolated event. However, the available source describes the risks broadly and does not establish one specific pollutant, exposure threshold, or outcome as definitive. This underscores the difficulty of drawing simple conclusions from complex, combined exposures.

Ambient and Household Exposure

Research has examined both ambient and household particulate pollution in relation to perinatal health outcomes. Rakesh Ghosh and co-workers reported associations between particulate-matter air pollution and adverse perinatal outcomes. Separately, a 2022 study analyzed the independent and joint effects of multiple household air-pollution sources on preterm birth among 63,038 mother–child pairs from the Longhua Child Cohort Study in 2017. Together, these studies show that comparisons may need to account for both outdoor particulate exposure and combined household sources.

These findings suggest that household air pollution, specifically PM2.5 and CO, may disrupt normal placental vascular development, leading to fetal thrombosis. This, in turn, can compromise nutrient and oxygen supply to the fetus, potentially contributing to low birth weight and stillbirth. While the study did not definitively establish a causal relationship, it provides compelling evidence of a concerning link.

Protecting Your Pregnancy: Practical Steps to Reduce Household Air Pollution Exposure

While the study highlights a serious concern, it also empowers expectant mothers to take proactive steps to mitigate their risk. If you rely on biomass fuels for cooking or heating, consider these practical measures to reduce your exposure to household air pollution. While larger studies are needed to confirm the findings, minimizing exposure to smoke is a prudent step for every pregnant woman.

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Risk in Real Life

Air-pollution research on pregnancy must account for more than pollutant levels alone. The MACE birth cohort study considered sociodemographic, behavioral, physical-activity, and clinical prenatal factors when investigating adverse birth outcomes associated with ambient air pollution exposure. Its design reflects how real-world pregnancy risks are shaped by overlapping personal and environmental conditions. Adjusting for these factors is therefore important when interpreting associations between exposure and birth outcomes.

How particulate exposure relates to different birth measures

Proposed biological pathways include pollutants crossing the placenta or affecting maternal lung function; particulate exposure is also described as inducing maternal and placental oxidative stress and inflammation. These mechanisms offer context for associations with fetal growth, but do not establish that a pathway explains a particular birth outcome.[1] [2]

What remains unresolved about exposure and birth outcomes

  • How much do differences in exposure assessment, exposure levels, and adjustment for confounding account for the variation among reported results?[3]
  • Why does the evidence for low birth weight differ between term births and all births, and across studies with substantial heterogeneity?[4]
  • How do the proposed placental and maternal pathways relate to the observed differences in birth weight, head circumference, and birth length?[1] [2] [5]

Sources

  1. Household Air Pollution from Solid Fuel Use and Risk of Adverse Pregnancy Outcomes: A Systematic Review and Meta-Analysis of the Empirical Evidence (pmc.ncbi.nlm.nih.gov)
  2. Household polluting cooking fuels and adverse birth outcomes: An updated systematic review and meta-analysis (pmc.ncbi.nlm.nih.gov)
  3. Ambient and household PM2.5 pollution and adverse perinatal outcomes: A meta-regression and analysis of attributable global burden for 204 countries and territories (pmc.ncbi.nlm.nih.gov)
  4. Prenatal exposure to particulate matter and term low birth weight: systematic review and meta-analysis (pmc.ncbi.nlm.nih.gov)
  5. The associations of air pollution exposure during pregnancy with fetal growth and anthropometric measurements at birth: a systematic review and meta-analysis. (pubmed.ncbi.nlm.nih.gov)

About this Article -

Written with AI assistance from published research, and reviewed by the Mystum team. See our About page for more information.

Everything You Need To Know

1

What specific household pollutants should pregnant women be most concerned about, and why?

Pregnant women should be particularly concerned about fine particulate matter (PM2.5) and carbon monoxide (CO) from household sources. These pollutants, released when burning solid biomass fuels like wood or charcoal for cooking and heating, have been linked to adverse pregnancy outcomes. PM2.5 and CO can disrupt normal placental vascular development, potentially leading to fetal thrombosis, which compromises nutrient and oxygen supply to the fetus.

2

What is Fetal Thrombotic Vasculopathy (FTV), and how might household air pollution contribute to it?

Fetal Thrombotic Vasculopathy (FTV) is a condition affecting the blood vessels in the placenta. The study suggests a link between exposure to PM2.5 and CO from household air pollution and an increased risk of FTV. Exposure to these pollutants may disrupt normal placental vascular development, leading to fetal thrombosis. This can compromise the placenta's ability to provide adequate nutrients and oxygen to the developing fetus, potentially contributing to complications like low birth weight or stillbirth. While the study did not establish a direct causal relationship, the association is concerning.

3

The study mentions it did not find a direct link between air pollution and general inflammation or hypoxia. Why is this significant, and what does it tell us about how air pollution might be affecting pregnancies?

The lack of a statistically significant association between household air pollution exposure and general inflammatory or hypoxic placental lesions suggests that the mechanism through which PM2.5 and CO affect pregnancy outcomes may be more specific than initially hypothesized. It indicates that the pollutants might be directly impacting the development and function of placental blood vessels, leading to Fetal Thrombotic Vasculopathy (FTV), rather than causing widespread inflammation or oxygen deprivation. This finding is important because it helps narrow down the potential biological pathways through which household air pollution exerts its harmful effects on fetal development, allowing for more targeted interventions.

4

What were the average levels of PM2.5 and CO exposure in the study conducted in Dar es Salaam, and how do they compare to World Health Organization (WHO) guidelines?

In the Dar es Salaam study, the average PM2.5 exposure was 40.5 µg/m³, and a significant 88.6% of measurements exceeded World Health Organization (WHO) air quality guidelines. The average CO exposure was 2.21 ppm. These levels indicate that the pregnant women in the study experienced moderate household air pollution. The fact that most PM2.5 measurements surpassed WHO guidelines highlights the concerning nature of household air pollution in the study area and underscores the potential risk to pregnancy health.

5

If I rely on biomass fuels for cooking or heating, what are some immediate steps I can take to reduce my exposure to household air pollution during pregnancy, even if larger studies are still needed to confirm the research findings?

Even before larger studies confirm the findings, minimizing exposure to smoke is a prudent step for every pregnant woman. If you rely on biomass fuels, ensure proper ventilation in your cooking and heating areas. This might involve opening windows and doors or using a range hood to vent smoke outside. Consider using cleaner-burning stoves or fuels, if feasible. Spend more time in areas with cleaner air, and explore options for air purification, particularly during periods of heavy cooking or heating. Although the article does not provide additional solutions, you should seek advice from healthcare providers on potential options.

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