preterm birth

Wildfire Smoke Exposure During Pregnancy Linked to Higher Risk of Preterm Birth, ECHO Study Finds

Posted on by Jodi Snare

Study highlights increased risk, especially in Western states and during intense smoke events

Exposure to wildfire smoke during pregnancy was associated with a higher risk of preterm birth, especially in the Western United States and during periods of intense or prolonged smoke, according to a study funded by the National Institutes of Health’s Environmental influences on Child Health Outcomes (ECHO) Program.

Wildfires are becoming more frequent and severe, raising concerns about their impact on public health. While previous studies suggested a link between wildfire smoke and preterm birth, ECHO’s research built on this by studying a diverse population from prospective cohort sites nationwide. Researchers also looked closely at the role of exposure intensity, duration, and timing.

“Our study adds to growing evidence that wildfire smoke is a concern for maternal and child health. Incorporating wildfire smoke considerations into prenatal care and public health guidance could help expecting parents protect themselves during smoke events, especially in areas where wildfires are common,” said Allison Sherris, PhD, of the University of Washington.

Researchers analyzed data from over 20,000 births between 2006 and 2020 at 30 study sites across the U.S. They matched daily levels of air pollution from wildfire smoke (fine particulate matter, or PM2.5) to each participant’s home address during pregnancy. They tracked both the average amount of smoke and the number of “smoke days,” as well as “smoke waves”—stretches of consecutive days with high smoke levels.

The team used statistical methods to compare pregnancies week by week and adjusted for many factors, including maternal age, race, ethnicity, neighborhood poverty, season of conception, birth year, and more.

Key Findings

  • Widespread Exposure: Nearly all pregnant participants (99.2%) experienced at least one day of wildfire smoke, with an average of 22 smoke days during pregnancy.
  • Preterm Birth Risk: The overall rate of preterm birth was 8.4%, with higher rates among Black (11.7%) and American Indian or Alaska Native (13.5%) participants compared to White (7.6%) and Asian, Native Hawaiian, or Pacific Islander (8.0%) participants.
  • Link Between Smoke and Preterm Birth: For every 1 microgram per cubic meter (µg/m³) increase in average wildfire PM2.5 during pregnancy, the odds of preterm birth increased by about 7%. The association was even stronger in the Western U.S., where wildfire smoke is more intense and frequent.
  • Intensity and Duration Matter: The risk of preterm birth was higher with more intense smoke and longer-lasting smoke events. The strongest associations were seen for mid-pregnancy exposure to lower levels of smoke and late-pregnancy exposure to high-intensity smoke days.
  • Critical Windows of Vulnerability: Certain periods during pregnancy—especially mid-pregnancy for lower-intensity smoke and late pregnancy for high-intensity smoke—were linked to the greatest risk increases for preterm birth.

“Preterm birth has strong implications for future child health. Better understanding of how to prevent preterm birth will pay off as a healthier population into the future,” said Catherine Karr, MD, PhD, of the University of Washington.

The study points to the need for more research on why some regions or groups may be more affected, how wildfire smoke combines with other risks like extreme heat, and which prevention strategies work best. It also highlights the importance of public health agencies and healthcare providers offering ways to help keep pregnant people safe during wildfire events.

This collaborative research was published in The Lancet Planetary Health.

About ECHO
The ECHO Cohort Consortium is a research program supported by the National Institutes of Health (NIH) with the mission to enhance the health of children for generations to come. ECHO Cohort investigators study the effects of a broad range of early environmental influences on child health and development. For more information, visit echochildren.org.

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Wildfire Smoke Exposure May Be Linked to Higher Risk of Preterm Birth, ECHO Study Finds

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Wildfire Smoke Exposure May Be Linked to Higher Risk of Preterm Birth, ECHO Study Finds

Authors: Allison Sherris, et al.

 

Who sponsored this study?

The Environmental influences on Child Health Outcomes (ECHO) Program, Office of the Director, National Institutes of Health supported this research.

 

Why was this study needed?

Wildfire smoke exposure is a growing threat to public health in the United States. The fine particulate matter (PM2.5) in wildfire smoke may be more harmful than other kinds of ambient air pollution because of the chemicals it’s made of and how these chemicals interact with the body. Pregnant women and the developing fetus may be particularly sensitive to the effects of wildfire PM2.5. Previous studies have associated wildfire smoke with preterm birth. This study builds on previous work by including a large number of participants from across the country, accounting for other risk factors, and looking closely at how the timing, intensity, or duration of smoke exposures affects birth outcomes.

 

What were the study results?

Nearly all pregnant participants (99.2%) experienced at least one day of wildfire smoke, with an average of 22 smoke days during pregnancy. The study found that higher average wildfire smoke exposure during pregnancy was linked to a slight increase in risk for preterm birth. The connection was clearer in the Western U.S., especially with more intense or longer-lasting smoke events. Preterm birth was also associated with exposure to smoke days in mid-to-late pregnancy at the national level.

 

What was this study's impact?

The study highlighted that exposure to wildfire-specific PM2.5, particularly at higher intensities and durations, is a risk factor for preterm birth. This is especially relevant in the Western U.S., where associations were more pronounced.

 

Who was involved?

The study included 20,034 pregnant participants who gave birth between 2006 and 2020, recruited from 30 ECHO Cohort Study Sites with residences during pregnancy in all 48 contiguous US states and the District of Columbia across the U.S.

 

What happened during the study?

The study tracked how much wildfire smoke pregnant participants were exposed to based on where they lived. Researchers looked at both the amount and duration of smoke, including stretches of smoky days in a row. They then used statistical methods to see if greater smoke exposure was linked to a higher risk of preterm birth, while also accounting for other health and social factors.

Footnote: Results reported here are for a single study. Other or future studies may provide new information or different results. You should not make changes to your health without first consulting your healthcare professional.

 

What happens next?

Future research could help identify regional differences in the effects of wildfire exposure, how wildfire smoke interacts with other risks like extreme heat, which parts of the smoke are most harmful, and how well different prevention strategies work to reduce exposure and related health outcomes.

 

Where can I learn more?

Access the full journal article, titled “Wildfire-specific fine particulate matter and preterm birth: a US ECHO Cohort analysis,” in Lancet Planetary Health.

The content is the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

 

Published November 3, 2025

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Wildfire Smoke Exposure May Be Linked to Higher Risk of Preterm Birth, ECHO Study Finds

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Pre-, Peri-, and Postnatal

ECHO Participants and Investigators Featured in The Washington Post

Posted on by Jodi Snare

The Washington Post recently featured the Environmental influences on Child Health Outcomes (ECHO) Program in a story on phthalates—chemicals commonly found in plastics and personal care products—and how they may affect babies’ development during pregnancy.

The article highlighted ECHO participants who are helping researchers understand how chemical exposures during pregnancy and throughout the life course may influence pregnancy outcomes and child health. ECHO participants Arica Nyamsi and Cassondra Perez shared a range of experiences with chemical exposures, from making significant lifestyle changes to expressing uncertainty and a need for clearer guidance.

Sheela Sathyanarayana, a professor of pediatrics at the University of Washington, explained that determining safe levels of phthalate exposure is challenging because individual health risks vary based on genetics and susceptibility.

The story also featured ECHO investigator Dr. Leonardo Trasande of NYU Grossman School of Medicine, who noted in the article:

“Endocrine-disrupting chemicals are one of the biggest global health threats of our time. And 2 percent of us know about it — but 99 percent of us are affected by it.”

Chemical exposures will be a focus at the ECHO Symposium: Translating Science to Action on September 15, 2025. During the first session, Dr. Trasande will discuss phthalate exposure in pregnancy and early childhood, focusing on the evidence, knowledge gaps, and opportunities to inform policies, practices, and programs. Mrs. Perez will also speak during the third session on her experience as an ECHO participant.

Learn more about ECHO’s ongoing research on chemical exposures. Also, review the full symposium agenda for details and register to attend this free event either in-person or virtually.

Pregnancy Diet Patterns and their Associations with Birth Outcomes Differ Across Racial and Ethnic Groups

Posted on by Jodi Snare

Dietary patterns during pregnancy can affect maternal blood sugar levels and birth outcomes, with important differences depending on racial and ethnic backgrounds, according to a recent ECHO Cohort study led by Luis E. Maldonado, PhD, MPH, of the University of Southern California.

Which combination of foods most influences blood sugar and birth outcomes during pregnancy remains unclear, especially across different racial and ethnic groups. Studying these differences is important because, although diet is known to affect birth outcomes, variations in dietary patterns may help explain disparities—for example, Hispanic women in the U.S. face higher rates of preterm birth and low birthweight compared to non-Hispanic White women.

“Our findings show it’s important to look at how diet affects birth outcomes in different racial and ethnic groups separately, especially in diverse communities,” said Dr. Maldonado. “Combining all racial and ethnic groups into one might hide important differences in how diet relates to birth outcomes for each group.”

Researchers analyzed data from over 980 pregnant women—420 Hispanic and 564 non-Hispanic White participants—from two ECHO Cohort study sites. Their aim was to identify how different combinations of food related to blood sugar and birth outcomes such as preterm birth and low birthweight.

Key takeaways

  • Diets high in refined grains (like white bread or white rice) and low in whole grains were linked to babies being born earlier, smaller, or with low birthweight.
  • Analyzing dietary patterns within specific racial and ethnic groups revealed stronger associations with negative birth outcomes than when looking at the combined group.
  • Among non-Hispanic White women, whole grains were most strongly associated with better blood sugar control.
  • Fruit was linked to higher blood sugar levels among Hispanic participants.
  • Solid fats and nuts and seeds were associated with lower blood sugar levels in both groups.

The study underscores the value of considering dietary patterns separately within racial and ethnic groups to better understand how diet affects pregnancy outcomes. Future research can build on these findings by continuing to explore culturally relevant dietary patterns in diverse populations, helping uncover associations that may be missed in broader, combined analyses.

This collaborative research, titled “Racial/Ethnic-Derived Maternal Diets Predict Birth Outcomes Better than a Diet Derived from a Combined Sample among Hispanic/Latina and non-Hispanic White Pregnant Individuals in the ECHO Cohort,” in Nutrition.

A Diet High in Refined Grains and Low in Whole Grains in Pregnancy Linked to Lower Birthweights and Pre-term Births

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A Diet High in Refined Grains and Low in Whole Grains in Pregnancy Linked to Lower Birthweights and Pre-term Births

Analyzing Diets Based on Racial and Ethnic Groups May Better Predict Outcomes

Authors: Luis E. Maldonado, et al.

 

Who sponsored this study?

The Environmental influences on Child Health Outcomes (ECHO) Program, Office of the Director, National Institutes of Health supported this research.

 

Why was this study needed?

Researchers wanted to understand how a pregnant person’s diet, especially in relation to their blood sugar levels (fasting blood glucose), affects birth outcomes—like the baby’s weight and whether the baby is born early. Higher fasting blood glucose during pregnancy is known to increase the risk of adverse birth outcomes. However, little is known about whether culturally influenced combinations of foods and beverages play a meaningful role across different racial and ethnic groups. This question is important because, in the U.S., Hispanic pregnant women are disproportionately affected by adverse birth outcomes, such as preterm birth and low birthweight (under 5.5 pounds). By examining dietary patterns within racial and ethnic groups, the researchers aimed to uncover more precise links between diet and birth outcomes. These links might be overlooked when analyzing the population as a whole, since average diets often reflect the eating patterns of the most represented groups in the study.

 

What were the study results?

Refined grains, such as white bread or white rice, showed the strongest association with higher fasting blood sugar levels among Hispanic and non-Hispanic White women. People who ate diets high in refined grains and low in whole grains were more likely to have babies born with low birthweight, smaller for gestational age, or born preterm.

When dietary patterns were analyzed by racial and ethnic group, the associations between diet, blood sugar, and birth outcomes were stronger than when using a single pattern for the full population. In the group that included non-Hispanic White and Hispanic participants, nuts, seeds, and solid fats such as butter and lard were linked to lower blood sugar. Among non-Hispanic White participants, whole grains and solid fats had the strongest association with improved blood sugar control. In contrast, among Hispanic participants, higher fruit consumption was associated with elevated blood sugar levels. These food-specific associations should be considered within the overall dietary pattern, as individual foods can influence blood sugar – beneficially or adversely – within the broader diet.

 

What was the study's impact?

The results of this study show the importance of looking at dietary patterns within racial and ethnic groups, particularly in studies with varying representation of different racial and ethnic populations. Analyzing a single, combined group may mask group-specific associations between diet and birth outcomes, as the effects of diet can differ across racial and ethnic backgrounds.

 

Who was involved?

The study included 420 Hispanic and 564 non-Hispanic White pregnant participants from two ECHO Cohort study sites.

 

What happened during the study?

During the study, participants shared details about what they ate over a 24-hour period. The researchers analyzed the diets, along with the mother’s blood sugar, to help determine which combinations of foods eaten together in an overall diet are most closely linked to changes in blood sugar levels. They then tested whether the links between diet and birth outcomes were different across racial and ethnic groups by comparing findings from diets derived using group-specific versus combined fasting blood glucose, which have also been previously shown to vary by racial and ethnic population.

Footnote: Results reported here are for a single study. Other or future studies may provide new information or different results. You should not make changes to your health without first consulting your healthcare professional.

 

What happens next?

Future research could continue exploring how dietary patterns affect birth outcomes in diverse populations, especially by identifying patterns that are specific to different racial and ethnic groups.

 

Where can I learn more?

Access the full journal article, titled “Racial/Ethnic-Derived Maternal Diets Predict Birth Outcomes Better than a Diet Derived from a Combined Sample among Hispanic/Latina and non-Hispanic White Pregnant Individuals in the ECHO Cohort,” in Nutrition.

 

The content is the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Published June 12, 2025

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A Diet High in Refined Grains and Low in Whole Grains in Pregnancy Linked to Lower Birthweights and Pre-term Births

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Pregnancy and birth

ECHO Study Investigates Pollution Exposure and Birth Outcomes in Pregnant Women Living in Historically Redlined Neighborhoods

ECHO Study Investigates Pollution Exposure and Birth Outcomes in Pregnant Women Living in Historically Redlined Neighborhoods

Authors: Teresa Herrera, Akhgar Ghassabian, et al.

 

Who sponsored this study?

The Environmental influences on Child Health Outcomes (ECHO) Program, Office of the Director, National Institutes of Health supported this research.

 

Why was this study needed?

Exposure to tiny air pollutants known as PM2.5 during pregnancy can lead to outcomes like low birth weight and preterm birth. Factors such as weather, government policies, and social conditions can affect how much exposure pregnant women have to these pollutants. One factor that may have affected exposure is redlining, the historical practice of designating certain neighborhoods, often where minority groups lived, as risky investments for lenders. This grading system ranked neighborhoods on an A through D scale—A being the most desirable—which often led to disinvestment and lack of resources in lower-rated areas. While redlining was made illegal following the 1968 Fair Housing Act, it continues to affect the health outcomes of people living in historically redlined areas.

ECHO researchers wanted to learn whether living in historically redlined areas during pregnancy affects air pollution exposure and birth outcomes in New York City (NYC). Understanding what influences PM2.5 levels and their impact on birth outcomes can help improve the health of mothers and their children.

 

What were the study results?

The study found that living in lower-graded or ungraded census tracts during pregnancy was associated with higher exposure to PM2.5. These women also tended to have babies with lower birth weights. This association was strong even when considering factors such as race, ethnicity, and income at individual and community levels.

 

What was this study's impact?

The study supports the literature linking redlining to contemporary outcomes. This study highlights the multifaceted nature of structural racism. Findings from non-graded areas indicate that there are likely additional factors, along with redlining, that play a role in perpetuating modern-day inequality.

 

Who was involved?

The participants were 3,160 pregnant mothers and their babies in the NYC metropolitan area who were enrolled in six ECHO Cohort research sites. The study included pregnant mothers from 2005 to 2022 who had air pollution estimates available for their residential address. Most participants who identified as Black or White lived in neighborhoods that had been given a D grade, the lowest rating. Most participants who identified as Hispanic lived in neighborhoods with B or C grades.

 

What happened during the study?

Researchers used statistical methods to explore whether living in neighborhoods that were historically redlined was associated with higher exposure to air pollution (PM2.5) during pregnancy. They also examined if living in these neighborhoods was associated with the baby's birth weight, the likelihood of being born early, and the chances of having a low birth weight.

Note: Results reported here are for a single study. Other or future studies may provide new information or different results. You should not make changes to your health without first consulting your healthcare professional.

 

What happens next?

The authors note that future research could look at other practices like racial exclusionary zoning to fully understand the ongoing systemic effects of redlining.

 

Where can I learn more?

Access the full journal article, titled “Redlining in New York City: Impacts on Particulate Matter Exposure During Pregnancy and Birth Outcomes,” in Journal of Epidemiology and Community Health.

The content is the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

 

Published September 5, 2024

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ECHO Study Investigates Pollution Exposure and Birth Outcomes in Pregnant Women Living in Historically Redlined Neighborhoods

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ECHO Study Evaluates Influence of Neighborhood-Level Poverty and Food Insecurity During Pregnancy on Birthweight

Authors: Izzuddin Aris, Emily Oken, et al.

Weight Gain During Infancy in Children Born Preterm Associated with Higher Risk of Obesity, According to New ECHO Research

Authors: Michael O’Shea, et al.

ECHO Study Suggests No Association Between Maternal Stress in the First Year After Birth and Childhood BMI

Authors: Callie Brown, Charles Wood, et al.

Depression in New Mothers Is Common, Especially When Babies Are Born Too Early

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Depression in New Mothers Is Common, Especially When Babies Are Born Too Early

Author(s): Nicole Bush, Danielle Roubinov, Rashelle Musci, et al.

 

Who sponsored this study?

This research was supported by the Environmental influences on Child Health Outcomes (ECHO) program, Office of The Director, National Institutes of Health.

Footnote: The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

 

What were the study results?

During the first five years following childbirth, one out of every five mothers who gave birth to a preterm baby had symptoms of depression, while one out of every ten mothers who gave birth to a full-term baby had symptoms of depression. For mothers of preterm infants, it was also more common to have symptoms that got worse over time compared to women who gave birth to full-term babies. The most severe symptoms of depression were seen in women who gave birth early.

Footnote: Results reported here are for a single study. Other or future studies may provide new information or different results. You should always consult with a qualified healthcare provider for diagnosis and for answers to your personal questions.

 

What was the study's impact?

This study supports previous reports that many mothers struggle with their mental health after giving birth, and women who have preterm babies may be particularly at risk for symptoms of depression—such as sadness, stress, anxiety, and feelings of being overwhelmed. Maternal mental health can influence their child’s health and development. Right now, doctors only screen women for depression symptoms when they are pregnant and for six months after they have their babies. This study shows that some women continue to struggle with depression for years after they give birth or start experiencing depression when their children are older. This trend was especially true for women whose babies were born prematurely. This study shows the importance of asking women about their mental health for much longer than six months after they give birth and helping them find supportive interventions.

 

Why was this study needed?

The postpartum period can be especially hard for mothers when babies are born prematurely, but researchers don’t know much about the effect that preterm births can have on a mother’s mental health. This study assessed postpartum depressive symptom trajectories for mothers of preterm and full-term babies, and followed participating mothers for five years after birth to better understand the long-term risks for depression and potential opportunities for treatment.

 

Who was involved?

The study involved 11,320 pregnant women aged 18 to 52 years old from 35 ECHO cohorts across the United States. About 11% of these women had babies that were born before they were due (preterm infants) and 89% had babies that were born on or near their due date (full-term infants).

 

What happened during the study?

Researchers analyzed self-reported depression measurements for women when they were pregnant and after they had their babies. These women also completed at least one follow-up assessment before their children were 5 years old.

 

What happens next?

It is important for future research to study what factors put some women at higher risk of experiencing depression after giving birth, particularly mothers of premature babies. Future research should also investigate what types of programs can help support mothers and their mental health during pregnancy and after birth.

 

Where can I learn more?

Access the full journal article titled, “Trajectories of Depressive Symptoms Among Mothers of Preterm and Full-Term Infants in a National Sample” in Archives of Women's Mental Health.

The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Published June 16, 2022

 

Access the associated article.

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Depression in New Mothers Is Common, Especially When Babies Are Born Too Early

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