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E2A: Wildfire Smoke & Pregnancy

Can Wildfire Smoke Hurt my Baby?

Educational Tools and Posters for You and Your Clinic

Click on the thumbnail below or right-click ‘save as’ to download the educational material.

Download this poster “Wildfire Smoke and Pregnancy” to place in waiting rooms, examining rooms and teaming rooms.

Bottom Line

Pregnant individuals are uniquely vulnerable to the health impacts of climate change. Emerging evidence suggests that wildfire smoke exposure during pregnancy may increase the risk of adverse maternal and infant health outcomes, including preterm birth, low birth weight, hypertensive disorders of pregnancy, and mental health impacts. In recognition of these risks, the 2022 Intergovernmental Panel on Climate Change (IPCC) identified pregnant individuals as a population particularly vulnerable to climate change.1
While additional research is needed, healthcare providers can play an important role in supporting pregnant individuals to reduce wildfire smoke exposure, prepare for periods of poor air quality, and address both the physical and mental health impacts of wildfire events.
For practical strategies to reduce exposure to wildfire smoke and air pollution, please refer to the Wildfire Smoke Campaign, which complements this campaign and provides additional resources for healthcare providers and patients.

Evidence

Pregnant individuals may be particularly vulnerable to wildfire smoke exposure due to physiological changes in pregnancy, including increased respiratory rate, increased oxygen demand, cardiovascular adaptations, and heightened susceptibility to stress-related mental health impacts. Wildfire smoke contains fine particulate matter (PM2.5), carbon monoxide, ozone, and other pollutants that may contribute to inflammation, oxidative stress, and vascular dysfunction, all of which have been implicated in adverse pregnancy outcomes.

Evidence linking wildfire smoke exposure to adverse perinatal outcomes is growing, although limitations in exposure measurement and study design remain. A 2024 systematic review and meta-analysis of 31 studies found suggestive evidence that wildfire smoke exposure during pregnancy may be associated with reduced birth weight, low birth weight, preterm birth, and other adverse maternal and child health outcomes. Five sufficiently comparable studies were included in the birth-weight meta-analysis, which estimated a 16.18-gram reduction in birth weight for every 5 µg/m³ increase in wildfire-related PM₂.₅ . A separate pooled analysis of four studies estimated a 21% higher likelihood of low birth weight.2

Several large observational studies have demonstrated associations between wildfire smoke exposure and adverse pregnancy outcomes. A California study estimated that each additional day of wildfire smoke exposure during pregnancy was associated with a 0.49% increase in the risk of preterm birth, with median exposure translating to approximately a 3.4% increased risk compared with unexposed pregnancies.3 A Colorado cohort study reported increased odds of preterm birth (OR 1.32) and gestational hypertension (OR 1.15–1.20) among individuals exposed to wildfire-related PM2.5 during pregnancy. Additional evidence suggests exposure to air pollutants may contribute to biological pathways associated with preeclampsia through alterations in placental angiogenic markers.4
Pregnancy is a period of increased vulnerability to anxiety, depression, and stress-related disorders. Climate-related disasters such as wildfires can compound these risks through displacement, loss of housing, disruption of social supports, and ongoing uncertainty. Following the 2016 Fort McMurray wildfire, studies reported substantial psychological distress among pregnant and preconception individuals, while higher levels of social support were associated with greater resilience and lower symptom severity.5

Most available evidence is observational and cannot establish causation. Exposure assessment methods vary between studies, and more research is needed to better understand critical exposure windows, dose-response relationships, and long-term maternal and child health outcomes.

Why Does It Matter?

Why are Pregnant Individuals Vulnerable to Climate Change?

Pregnant women are relatively more vulnerable to the impacts of climate change due to gender inequities and physiologic changes that may impact their health and the health of their babies. The United Nations Development Programme (UNDP) module on Gender and Climate Change highlights that we must use a gendered lens when looking at climate change and understand that there is significant gender inequity.6

  • Climate change disproportionately kills more women than men
  • The majority of people displaced from climate change are women

Pre-existing gender inequities are exacerbated by climate change. Women are found to be particularly vulnerable due to:

  • Less access to crucial resources
  • Structural inequality: pre-existing male dominated decision-making structures
  • Less access and understanding of technology
  • Gendered cultural expectations: expectation of caring and protecting the family, not equipped with same level of survival skills.6 7 8 The majority of global populations living in conditions of poverty and those in charge of the poorest households are women 6 7 9

 

Scripts

Consider one short script to use with patients who are climate aware and one script to use for patients who may be resistant to discussing climate issues.

We're heading into wildfire season, so I was hoping to spend a few minutes talking about smoke exposure. Some studies suggest that significant smoke exposure during pregnancy may be associated with complications such as preterm birth or high blood pressure, although we're still learning more about these risks. Let's review a few practical things you can do to protect yourself and your baby if smoke levels become high."

One thing we learned from previous wildfire events is that social support can make a big difference during stressful situations. If there were prolonged smoke exposure or an evacuation, do you have family, friends, or community supports you could rely on? It's helpful to think about these things before an emergency happens."

Deeper Dive:

Review of the Physiologic Changes of Pregnancy

Consider the physiological changes that make pregnant individuals more susceptible, at baseline, to the health effects of wildfire smoke pollution:

1. Respiratory changes:
  • Increase respiratory rate (RR) and tidal volume (TV)
  • Increased levels of the hormone progesterone, leading to greater sensitivity to changes in PaCO₂ and therefore a lower threshold to breathe, which may contribute to increased dyspnea
2. Cardiovascular changes:
  • Increase in cardiac demand:
    • CO (cardiac output) = SV x HR
      In pregnancy stroke volume (SV) increases and heart rate (HR) may marginally increase
    • Systemic vascular resistance (SVR) is lower and thus there is decreased afterload effect
  • SVR decrease is multi-factorial:
    • Hormonal effects such as increased progesterone
    • Low resistance uteroplacental circuit
  • Supine Hypotensive Syndrome (Aortocaval compression): in supine position, the gravid uterus can compress the IVC and aorta, leading to decreased CO and possible presyncopal symptoms
3. Perinatal mental health:
  • Period of increased risk of both exacerbating current disorders and developing new psychiatric conditions
  • Risk factors:
    • Lack of social supports and relationship discord
    • Stressful life events and financial stressor
    • Sleep deprivation, lack of exercise, and poor nutrition
    • Physiologic and hormonal changes of pregnancy

Postpartum blues (symptoms lasting up to 14 days): occurs in 50–85% of women and is associated with an increased risk of developing postpartum depression.10

  • In Canada, approximately 23% of mothers who gave birth in 2019 reported symptoms consistent with postpartum depression or anxiety.11 Climate change and wildfire smoke exposure may amplify this risk.

For a quick review of pregnancy physiology concepts please refer to this YouTube video:

Potential Pathophysiological Mechanisms of Wildfire Smoke

1. Inflammatory dysregulation
  • Disruption of the maternal–fetal immune balance may alter placental function and fetal development
  • Imbalances in pro- and anti-inflammatory mediators have been associated with preterm birth (PTB), fetal growth restriction (FGR), and preeclampsia
  • Wildfire smoke exposure has been linked to elevated inflammatory markers, including C-reactive protein (CRP) and changes in interleukin levels
2. Vascular dysregulation

Inflammation and oxidative stress may contribute to endothelial dysfunction. Potential consequences include vasoconstriction, reduced uteroplacental blood flow, and altered angiogenic signaling.

3. Increased oxidative stress

Increased production of reactive oxygen and nitrogen species may overwhelm antioxidant defenses. Resulting oxidative damage may impair normal placental and fetal development.

Wildfire Smoke (WS) is a complex mixture of particulate matter (PM), gases such as ozone (O3), carbon monoxide (CO), nitrogen dioxide (NO2), polycyclic aromatic hydrocarbons (PAHs), heavy metals, elemental and organic carbon, in addition to volatile and semi-volatile organic compounds.12

Examining the Acute and Chronic Perinatal Health Risks of Exposure to Wildfires

The section below highlights and summarizes the most recent and robust studies related to the perinatal health outcomes from exposure to wildfires. As this is an emerging field, more research is needed to better understand the significance of this relationship.

1. Low Birth Weight (LBW)

Brazilian cohort study (2010–2018) published in The Lancet Regional Health:13

  • Evaluated approximately 1.5 million live births and wildfire exposure across Brazil.
  • Excluded preterm births to specifically assess impacts on birth weight.
  • An increase of 100 wildfire events was associated with a higher risk of low birth weight.
  • The association was strongest among pregnancies exposed during the first trimester, with increased risks observed in both the South (18.55%) and Midwest (0.98%) regions of Brazil.
2. Pre-Term Birth (PTB)

Retrospective Study in California, analyzed all singleton births between 2006-2012 and estimated wildfire smoke exposure using satellite-derived smoke plume data and surface PM₂.₅ measurements.3

  • Results estimated that each additional day of wildfire smoke exposure during pregnancy was associated with 0.49% increased risk PTB
  • Median exposure in the sample was 7 days and translated to 3.4% increase compared to the unexposed
  • The effect varied by baseline smoke exposure: regions with less frequent wildfire smoke exposure showed a greater increase in PTB risk per additional smoke day than regions with more chronic smoke exposure
3. Gestational Hypertension (GHTN)

Retrospective cohort study (Colorado, 2007–2015): Analysis of approximately 535,895 singleton births examined associations between ambient wildfire-related PM₂.₅ exposure and adverse pregnancy outcomes.4

  • Preterm Birth (PTB):
    • Wildfire-related PM₂.₅ exposure during the second trimester was associated with a 32% increase in the odds of PTB after adjustment for confounding factors (OR 1.32).
    • Exposure across the entire pregnancy was associated with a 7.6% increase in the odds of PTB (OR 1.076).
    • Among individuals whose second trimester coincided with peak wildfire season, wildfire smoke exposure was associated with approximately 7.0% higher odds of PTB.
  • Gestational Hypertension (GHTN):
    • First-trimester wildfire smoke exposure was associated with a 14.8% increase in the odds of GHTN (OR 1.148)
    • Exposure across the entire pregnancy was associated with a 20.4% increase in the odds of GHTN (OR 1.204)
4. Preeclampsia

Prospective cohort study (Massachusetts, 2006–2008): included 1,066 pregnant individuals with singleton pregnancies who planned to deliver at the same teaching hospital. The study examined the longitudinal association between ambient air pollution exposure (PM₂.₅, O₃, and NO₂) and angiogenic biomarkers using serial blood and urine samples.14

Findings:

  • Previous research has demonstrated that individuals with preeclampsia typically have a higher ratio of soluble fms-like tyrosine kinase-1 (sFlt-1) to placental growth factor (PlGF)
  • Exposure to PM₂.₅ during early pregnancy was associated with an increased sFlt-1/PlGF ratio
  • Exposure to ozone (O₃) and nitrogen dioxide (NO₂) during late pregnancy was also associated with an increased sFlt-1/PlGF ratio

These findings suggest that air pollution exposure during pregnancy may contribute to angiogenic dysregulation, a biological pathway implicated in the development of preeclampsia. However, the study evaluated biomarkers rather than clinical preeclampsia outcome

The Impact of Environmental Stressors on Maternal Mental Health

The acute mental health impacts of extreme weather events such as wildfires and flooding have been widely studied. However, the effects of climate change on mental health often extend well beyond the immediate event. While visible impacts may fade over time, many stressors persist, including fear of future disasters, displacement, financial strain, and the gradual loss of meaningful places and routines. These less visible, chronic stressors can have lasting effects on psychological well-being. Pregnancy and the postpartum period represent times of increased physiological and psychological vulnerability. As a result, both the acute and chronic stressors associated with climate change may contribute to adverse maternal mental health outcomes. Recognizing and addressing these impacts is an important component of supporting maternal and child health. Studies show that:
  • Approximately 1 in 5 pregnant individuals in Canada experience anxiety or an anxiety-related disorder 15
  • In 2019, nearly 1 in 4 mothers who gave birth in Canada reported symptoms consistent with postpartum depression or anxiety 11
  • Pregnancy and the postpartum period are associated with an increased risk of both new-onset psychiatric conditions and exacerbation of pre-existing mental health disorders
  • Common risk factors include limited social support, relationship stress, financial hardship, stressful life events, sleep deprivation, physical inactivity, poor nutrition, and the physiological and hormonal changes associated with pregnancy
  • Postpartum blues affect approximately 50–85% of individuals after childbirth and typically resolve within the first 14 days postpartum. Individuals who experience postpartum blues may be at increased risk of developing postpartum depression
Additional Resource: UBC Perinatal Mental Health Infographic15

Let’s Consider the Fort McMurray Wildfire in 2016 in Northern Alberta

This was the largest evacuation to date in Alberta’s history, at least 88,000 people were forced from their homes. It is estimated that 8% of private residences were destroyed by the fire.5

Listen to this 1-minute CBC segment that showcases the new mothers and their children who survived the wildfire: https://www.cbc.ca/player/play/video/1.4104709

“A lot of these moms tried for so long and couldn’t conceive… and then to conceive and then have a baby… in the most traumatic thing of your life” 16

A study that was published in the Canadian Journal of Psychiatry in 2020, stated that out of the 88,000 evacuees, 1,850 were either pregnant or within 6 months before conception.17

  • Participants completed validated questionnaires assessing post-traumatic stress disorder (PTSD), resilience, and social support
  • Higher levels of peritraumatic distress and dissociative symptoms were associated with more severe PTSD symptoms
  • Greater satisfaction with social support was associated with lower PTSD symptom severity
  • However, social support did not appear to be protective among individuals with the most severe PTSD symptoms

A general population study examined the prevalence of mental health disorders among adults one year after the 2016 Fort McMurray wildfire.18

This study showed that:

  • Approximately 38% of evacuees met criteria for at least one probable mental health disorder, including: post-traumatic stress disorder (PTSD), major depressive disorder (MDD), generalized anxiety disorder (GAD), insomnia, and/or substance use disorder
  • A pre-existing mental health condition was a significant risk factor for all assessed mental health outcomes 

These findings suggest that the mental health impacts of wildfire-related disasters may persist long after the immediate event has ended, and that individuals with pre-existing mental health conditions may be particularly vulnerable to adverse psychological outcomes following wildfire exposure.

Applying the Ecological Grief Concept Through the Lens of a Pregnant Individual

1. Ecological Losses (“Slow Violence”)

Climate change often involves gradual, ongoing environmental changes rather than a single catastrophic event. During pregnancy, disruptions to one’s sense of place, connection to nature, or relationship with the local environment may contribute to feelings of sadness, grief, anxiety, helplessness, or hopelessness. Concerns about the long-term environmental and health consequences of wildfires may further intensify these emotional responses.19

2. Disruption of Environmental Knowledge and Sense of Identity

Environmental change can alter an individual’s relationship with familiar landscapes, communities, and cultural practices. For pregnant individuals, this may contribute to a loss of confidence in their ability to maintain their own well-being, raise a child in a healthy environment, or trust previously familiar surroundings and sources of support.

3. Anticipated Future Losses

Pregnancy often involves planning and hope for the future. Concerns about worsening wildfire seasons, environmental degradation, and climate-related risks may contribute to uncertainty, anxiety, and fear about the future. These feelings may be compounded by worries about the long-term health, safety, and quality of life of one’s children and future generations.

Lived Experiences of Pregnant Individuals During the Fort McMurray Wildfire

Bremault-Phillips et al. (2020) explored the experiences of pregnant individuals affected by the 2016 Fort McMurray wildfire through expressive writing narratives. Of the 54 participants, 56% were first-time mothers.19

A thematic analysis was conducted from the narratives that were gathered and found five key themes:20

  1. Stress Responses to Personal and External Factors
    Participants described significant emotional distress related to evacuation, uncertainty, wildfire smoke exposure, disruptions to birth plans, and concerns about the health and safety of their infants.
  2. Social Connectedness and Support as a Facilitator of Resilience
    Support from family, friends, healthcare providers, and the broader community was identified as an important protective factor that helped participants cope with the disaster.
  3. Engagement in Resilience-Building Activities
    Participants described drawing strength from community solidarity, helping others, maintaining routines, and focusing on recovery and adaptation.
  4. The Role of Pregnancy and Motherhood in Experiences of Loss and Resilience
    Wildfire-related disruptions affected important pregnancy, childbirth, and early parenting experiences. At the same time, concern for their children often served as a source of motivation and resilience.
  5. The Importance of Home and Place
    Participants expressed grief and distress related to displacement, loss of normalcy, and separation from their homes and communities. One participant stated: “I was so scared, confused and emotional. Our baby was less than a day old. We should be home.”

These findings highlight the unique challenges faced by pregnant individuals during wildfire-related disasters and emphasize the importance of social support, community connection, and trauma-informed approaches to promoting resilience and maternal mental health.

Attributions

Webcopy created by Drs. Keiko Patterson, Sonja Wicklum, Clark Svrcek, Rachelle Haddock and Jennifer Obeid from the Department of Family Medicine, University of Calgary Cumming School of Medicine, January 2026.

References:

1IPCC. Climate Change 2022: Impacts, Adaptation and Vulnerability Working Group II Contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. IPCC [Internet]. 2022;1(1). Available from: https://www.ipcc.ch/report/ar6/wg2/downloads/report/IPCC_AR6_WGII_FullReport.pdf↩

2Foo D, Stewart R, Heo S, Dhamrait G, Choi HM, Song YM, Bell ML. Wildfire smoke exposure during pregnancy and perinatal, obstetric, and early childhood health outcomes: a systematic review and meta-analysis. Environ Res. 2024;241:117527. doi:10.1016/j.envres.2023.117527↩

3Heft-Neal S, Driscoll A, Yang W, Shaw G, Burke M. Associations between wildfire smoke exposure during pregnancy and risk of preterm birth in California. Environ Res. 2022;203:111872. doi:10.1016/j.envres.2021.111872↩

4Abdo M, Ward I, O'Dell K, Ford B, Pierce J, Fischer E, et al. Impact of Wildfire Smoke on Adverse Pregnancy Outcomes in Colorado, 2007–2015. International Journal of Environmental Research and Public Health. 2019 Oct 2;16(19):3720.↩

5Government of Canada, Statistics Canada. Infographic: Fort McMurray 2016 Wildfire Economic Impact [Internet]. Statcan.gc.ca. 2016. Available from: https://www150.statcan.gc.ca/n1/pub/11-627-m/11-627-m2017007-eng.htm↩

6Habtezion S. Gender and Climate Change | United Nations Development Programme [Internet]. UNDP. 2017 [cited 2023 Apr 9]. Available from: https://www.undp.org/publications/gender-and-climate-change↩

7Sorensen C, Murray V, Lemery J, Balbus J. Climate change and women's health: Impacts and policy directions. PLOS Medicine [Internet]. 2018 Jul 10;15(7):e1002603. Available from: http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1002603↩

8Demetriades J, Esplen E, Brody A. The Gender Dimensions of Poverty and Climate Change Adaptation. IDS Bulletin. 2009 Jan 26;39(4):24–31.↩

9Osman-Elasha B. Women in the shadow of climate change. UN Chronicle. 2012 Apr 17;46(4):54–5.↩

10Balaram K, Marwaha R. Postpartum Blues. StatPearls [Internet]. 2023; Available from: https://www.ncbi.nlm.nih.gov/books/NBK554546/↩

11Government of Canada, Statistics Canada. The Daily — Maternal Mental Health in Canada, 2018/2019 [Internet]. Statcan.gc.ca. 2019. Available from: https://www150.statcan.gc.ca/n1/daily-quotidien/190624/dq190624b-eng.htm↩

12Basilio E, Chen R, Fernandez AC, Padula AM, Robinson JF, Gaw SL. Wildfire Smoke Exposure during Pregnancy: A Review of Potential Mechanisms of Placental Toxicity, Impact on Obstetric Outcomes, and Strategies to Reduce Exposure. International Journal of Environmental Research and Public Health. 2022 Oct 22;19(21):13727.↩

13Requia WJ, Amini H, Adams MD, Schwartz JD. Birth weight following pregnancy wildfire smoke exposure in more than 1.5 million newborns in Brazil: A nationwide case-control study. The Lancet Regional Health - Americas. 2022 Jul;11:100229.↩

14Zheng Y, McElrath T, Cantonwine D, Hu H. Longitudinal Associations between Ambient Air Pollution and Angiogenic Biomarkers among Pregnant Women in the LIFECODES Study, 2006–2008. Environmental Health Perspectives. 2023 Aug 1;131(8).↩

15Fairbrother N. Infographic on Anxiety in Pregnancy & the Postpartum | The Perinatal Anxiety Research Lab [Internet]. Med.ubc.ca. 2023. Available from: https://parlab.med.ubc.ca/infographic-on-anxiety-in-pregnancy-the-postpartum/↩

16Aww... Fort McMurray wildfire babies smile for the camera [Internet]. CBC. 2017 [cited 2025 Nov 25]. Available from: https://www.cbc.ca/player/play/video/1.4104709↩

17Verstraeten BSE, Elgbeili G, Hyde A, King S, Olson DM. Maternal Mental Health after a Wildfire: Effects of Social Support in the Fort McMurray Wood Buffalo Study. The Canadian Journal of Psychiatry. 2020 Nov 11;070674372097085.↩

18Belleville G, Ouellet MC, Morin CM. Post-Traumatic Stress among Evacuees from the 2016 Fort McMurray Wildfires: Exploration of Psychological and Sleep Symptoms Three Months after the Evacuation. International Journal of Environmental Research and Public Health [Internet]. 2019 May 1 [cited 2021 Jun 3];16(9). Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6540600/↩

19Brémault-Phillips S, Pike A, Olson J, Severson E, Olson D. Expressive writing for wildfire-affected pregnant women: Themes of challenge and resilience. International Journal of Disaster Risk Reduction. 2020 Nov;50:101730.↩

20Pike A, Mikolas C, Tompkins K, Olson J, Olson DM, Brémault-Phillips S. New Life Through Disaster: A Thematic Analysis of Women's Experiences of Pregnancy and the 2016 Fort McMurray Wildfire. Frontiers in Public Health. 2022 May 13;10.↩

21Muller B. Pregnancy becomes a more vulnerable time with climate change [Internet]. The Washington Post. 2022. Available from: https://www.washingtonpost.com/health/2022/04/11/climate-change-pregnancy-health-babies/↩