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 in Health & Wellness December 2025 • 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.

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.

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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Everything You Need To Know

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.

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.

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.

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.

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.