Exposure to Flame-retardant Chemicals During Pregnancy Associated with Differences in Child Growth Patterns

Authors: Anne P. Starling, Jessie P. Buckley, Deborah Bennett, 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?

Organophosphate esters (OPEs) are chemicals widely used as flame retardants and plastic softeners in a variety of household and industrial products. Pregnant women are commonly exposed to these chemicals. While prior studies have examined the effects of OPE exposure during pregnancy on birth outcomes, less is known about how prenatal exposure to these chemicals affects children’s growth patterns beyond infancy. Understanding how early-life environmental exposures are associated with child growth trajectories is important because childhood growth rates can be linked to later risk of obesity and heart disease. This study specifically examined the relationship between OPE exposure during pregnancy and child height, weight, and body mass index (BMI).

What were the study results?

The study found that exposure to specific OPEs during pregnancy was associated with differences in child growth rates between ages 2 and 10 years. Higher prenatal exposure to bis (1,3-dichloro-2-propyl) phosphate (BDCPP) was associated with faster increases in weight and height during early childhood (ages 2–5). In mid-childhood (ages 6–10), higher prenatal exposure to diphenyl phosphate (DPHP) was associated with faster increases in body mass index and weight. In contrast, prenatal exposure to bis(1-chloro-2-propyl) phosphate (BCPP) was associated with slower growth across multiple periods. Some associations differed by child sex and by maternal pre-pregnancy body mass index.

What was this study's impact?

These findings suggest that exposure to certain flame-retardant chemicals during pregnancy may be associated with children’s growth patterns. Because growth trajectories are linked to future obesity and metabolic health, these results underscore the importance of understanding and potentially reducing exposure to these widely used chemicals during pregnancy.

Who was involved?

The study included 4,566 mother-child pairs from 14 ECHO Cohort Study Sites across the United States. Researchers collected exposure data during pregnancy and collected growth data from ages 2 to 10 years.

What happened during the study?

Researchers measured nine chemical markers of OPE exposure in urine samples collected from pregnant participants. They later collected child weight and height measurements between ages 2 and 10 years, which were used to calculate each child’s BMI. The researchers then used statistical models to examine how prenatal OPE exposure was associated with rates of change in weight, height, and BMI.

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 studies could help researchers better understand the biological mechanisms linking prenatal OPE exposure to child growth and examine whether reducing exposure during pregnancy could improve long-term child health outcomes. Additional studies may also explore the combined effects of multiple environmental chemical exposures during pregnancy and early childhood on the patterns of child growth patterns.

Where can I learn more?

Access the full journal article, titled “Gestational exposure to organophosphate ester flame retardants and child growth in weight, height, and body mass index at age 2-10 years: the Environmental influences on Child Health Outcomes Program” in Environmental Research.

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

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Exposure to Flame-retardant Chemicals During Pregnancy Associated with Differences in Child Growth Patterns

Exposure to PM_2.5 Air Pollution During Pregnancy Associated with Lower Birthweight, ECHO Study Finds

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Exposure to PM_2.5Air Pollution During Pregnancy Associated with Lower Birthweight, ECHO Study Finds

Authors: Daniel Enquobahrie, Adaeze Wosu Nzegwu, 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 fine particulate matter (PM_2.5)—very small inhalable particles found in air pollution—is widespread and linked to various health risks. Previous research has examined the effects of PM_2.5exposure during pregnancy on birth outcomes, but gaps remain. More research is needed to understand whether there are critical windows during pregnancy when PM_2.5exposure is most impactful. This study aimed to address these gaps by investigating how the timing of PM_2.5exposure affects birth outcomes, such as birthweight and length of pregnancy, using data from the ECHO Cohort’s large, multi-site study structure. It also explored whether associations differ by infant sex and maternal race and ethnicity.

What were the study results?

Exposure to higher levels of PM_2.5during the first weeks of pregnancy was linked to babies being slightly smaller at birth and having a higher chance of being born small for their gestational age (smaller than average for the length of the pregnancy). There was no significant association between PM_2.5exposure and shorter pregnancies or preterm birth. For baby girls, higher PM_2.5exposure in early pregnancy seemed to affect their birth size more than for baby boys, suggesting that the baby's sex can make a difference in how air pollution affects growth. The effects of PM_2.5on birth outcomes like being born prematurely, birth size, or being small for gestational age varied depending on the mother's race and ethnicity.

What was this study's impact?

This study on PM_2.5 exposure during early pregnancy and birth outcomes can inform ongoing discussions on strategies for reducing PM_2.5 air pollution.

Who was involved?

The study included 19,108 mother-infant pairs from 51 ECHO Cohort Study Sites across the United States.

What happened during the study?

Researchers estimated PM_2.5 exposure for each pregnant participant based on residential address, accounting for moves during pregnancy. The researchers then assessed exposure for the whole pregnancy, each trimester, and specific windows in the first trimester. The researchers collected information on birth outcomes, including length of pregnancy and birthweight.

What happens next?

Further research could help investigators better understand the mechanisms underlying differences in air pollution vulnerability by infant sex, and by maternal race and ethnicity. Additional studies could also help researchers understand how other factors, such as diet and lifestyle, influence the relationship between PM_2.5exposure and birth outcomes.

Where can I learn more?

Access the full journal article, titled “Gestational fine particulate matter exposure and perinatal outcomes in the ECHO cohort: Associations across pregnancy windows,” in Environmental Research.

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

Published March 1, 2026

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Exposure to PM_2.5Air Pollution During Pregnancy Associated with Lower Birthweight, ECHO Study Finds

Exposure to Certain Flame-retardant Chemicals During Pregnancy May Be Linked with Decreased Cognitive Function in Young Children, ECHO Study Finds

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Exposure to Certain Flame-retardant Chemicals During Pregnancy May Be Linked with Decreased Cognitive Function in Young Children, ECHO Study Finds

Authors: 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?

Organophosphate esters (OPEs) are chemicals widely used as flame retardants and plastic softeners in a variety of household and industrial products, and previous studies suggest they can affect child brain development. With increasing human exposure to these chemicals, especially during sensitive periods like pregnancy, there has been concern about the potential impact on child cognitive development. Previous studies have found mixed results, highlighting the need for a large, contemporary cohort study to clarify these associations and examine possible sex differences.

What were the study results?

When pregnant women had higher urine levels of diphenyl phosphate (DPHP), a compound produced during the breakdown of certain OPEs in the human body, their children tended to have slightly lower scores on tests of mental skills at ages 4–6. This pattern was seen in boys and girls. Boys whose mothers had higher levels of certain other chemicals linked to OPE exposure during pregnancy scored higher on these tests, but this was not true for girls. This finding was unexpected, so more research may be needed to understand the biological mechanism underlying this association.

What was this study's impact?

Results from this large contemporary cohort of mother–child pairs in the U.S. suggest that OPE exposure during pregnancy may be associated with minor decreases in cognitive functioning in children. Considering that DPHP is a widely detected marker of OPE exposure in the U.S. population, the overall impact of this effect may be significant.

Who was involved?

The study included 831 mother–child pairs from three ECHO Cohort Study Sites in the United States. The study population was predominantly non-Hispanic White and highly educated, which may limit generalizability.

What happened during the study?

Pregnant participants provided urine samples for measurement of nine OPE chemicals. Researchers assessed child mental skills using standardized intelligence scales when children were between 4 and 6 years old. Researchers then used statistical analyses to examine associations between OPE exposure and childhood cognition.

What happens next?

Additional studies could help researchers better understand the biological pathways underlying these associations. Additional studies could also help clarify the association between some chemical markers of OPE exposure and higher cognitive scores among boys.

Where can I learn more?

Access the full journal article, titled “Prenatal exposure to organophosphate ester flame retardants and child cognition: findings from the environmental influences on child health outcomes cohort,” in Environmental Pollution.

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

Published February 1, 2026

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Exposure to Certain Flame-retardant Chemicals During Pregnancy May Be Linked with Decreased Cognitive Function in Young Children, ECHO Study Finds

ECHO Study Investigates Relationship Between Chemical Exposures, Pregnancy Stress, & Birth Outcomes

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ECHO Study Investigates Relationship Between Chemical Exposures, Pregnancy Stress, & Birth Outcomes

Authors: Stephanie Eick, Anne Dunlop, 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?

Most previous research on the effects of chemical exposures on birth outcomes has focused on a small number of well-established chemicals, such as bisphenol A (BPA) and certain phthalates. However, there are over 350,000 chemicals registered for global use, and the impact of many emerging or understudied chemicals on birth outcomes is not well understood. Additionally, prior studies have not adequately considered how different kinds of maternal stress (such as anxiety, depression, and adverse childhood experiences) might influence the effects of chemical exposures during pregnancy. This study examined a broader range of chemicals and evaluated the role of stress in influencing their associations with birth outcomes.

What were the study results?

Exposure to chemicals found in certain consumer and industrial products (such as phthalates, bisphenols, and insecticides) was associated with shorter pregnancies among women who experienced anxiety during pregnancy or in the early postpartum period. Depression modified how exposure to certain chemicals (such as phthalates, parabens, and insecticides) affected birthweight and length of pregnancy. Some chemicals positively correlated with length of pregnancy (duration) for mothers with more depression, while others were associated with lower birthweights when mothers had more depression symptoms. The study suggested that the effects of a mother’s stress on the relationship between chemical exposures and birth outcomes depended on the type of chemical and type of stressor experienced.

What was this study's impact?

This study found that exposure to chemicals commonly found in consumer products was associated with shorter pregnancies and lower among women experiencing anxiety during or after pregnancy. While the results were mixed, the researchers observed some patterns where effects of chemical exposures were strongest among mothers who experienced depression and anxiety. These findings suggest that screening for depression and anxiety during pregnancy could help identify women who may be at a higher risk of adverse birth outcomes.

Who was involved?

The study included 1,556 mother-child pairs from 11 ECHO Cohort Study Sites. 810 of these participants provided information on perceived stress, depression, and anxiety. Additionally, participants provided information on adverse childhood experiences.

What happened during the study?

Pregnant participants provided urine samples, which researchers analyzed for 113 chemicals from 10 chemical classes. Pregnant participants also reported on their stress, depression, anxiety, and adverse childhood experiences. Researchers collected information on each mother’s birth outcomes, including the length of their pregnancy (in weeks) and the baby’s birthweight. The researchers performed statistical analyses to examine associations between chemical exposures, stress, and birth outcomes.

What happens next?

Additional studies looking at the combined effects of multiple combined exposures could help researchers better understand the role of these factors in influencing birth outcomes. Future research could also further investigate potential biological effects of maternal adverse childhood experiences.

Where can I learn more?

Access the full journal article, titled “Psychosocial Stressors as Modifiers of the Associations Between Well-Studied and Understudied Chemicals and Birth Outcomes in the ECHO Cohort,” in Environmental Pollution.

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

Published January 15, 2026

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ECHO Study Investigates Relationship Between Chemical Exposures, Pregnancy Stress, & Birth Outcomes

Higher Early-Life PM_2.5 Linked to Higher Childhood Blood Pressure, While Prenatal NO₂ Exposure Associated with Lower Blood Pressure, ECHO Study Finds

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Higher Early-Life PM_2.5 Linked to Higher Childhood Blood Pressure, While Prenatal NO₂ Exposure Associated with Lower Blood Pressure, ECHO Study Finds

Authors: Yu Ni, Catherine Karr, 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?

The prevalence of high blood pressure (HBP) in children is rising globally, with long-term health consequences such as heart disease and impaired kidney function. Childhood high blood pressure has increased by nearly 80% over the past two decades, especially in countries with higher obesity rates like the United States. Since high blood pressure in childhood can both track into adulthood and affect children’s health directly, ECHO researchers wanted to understand the influence that environmental factors such as pollution can have on childhood blood pressure. Specific pollutants such as fine particulate matter (PM_2.5) and nitrogen dioxide (NO₂) are emitted from vehicles, power plants, and industrial processes. These pollutants are known contributors to heart disease in adults, but their impact on children’s blood pressure is less clear. Previous research has been inconclusive, often limited to single-site studies. Researchers used the ECHO Cohort’s large, multi-site study structure to help clarify these associations.

What were the study results?

Children who were exposed to more PM_2.5 air pollution before and after birth had slightly higher blood pressure on average between ages 5 and 12. Specifically, higher PM_2.5 exposure during the first trimester was linked to a more pronounced increase in systolic blood pressure and a greater risk of high blood pressure in childhood, indicating that early pregnancy may be a particularly sensitive period. When their mothers were exposed to more NO₂ air pollution during pregnancy, children unexpectedly had lower blood pressure. The study found that NO₂ exposure during mid- to late pregnancy was associated with slightly lower blood pressure levels, particularly in the second trimester, and was not linked to a higher risk of high blood pressure. These findings overall suggest that timing of pollution exposure during pregnancy matters for children’s blood pressure later in life.

What was this study's impact?

The study provides additional evidence that exposure to PM_2.5 may be associated with adverse effects on childhood cardiometabolic health, even at low exposure levels. The observed association between prenatal NO₂ exposure and decreased childhood blood pressure is unexpected and suggests that further research may be needed to better understand the underlying mechanisms as well as other environmental factors that may influence this relationship.

Who was involved?

The study included 4,863 U.S. children aged 5–12 years and their mothers, drawn from 20 ECHO Cohort Study Sites.

What happened during the study?

Researchers estimated how much outdoor air pollution children were exposed to at their homes, focusing on PM_2.5and NO₂. They examined exposure during each trimester of pregnancy, across the full pregnancy, and during the child’s first two years of life. Children’s blood pressure was measured between ages 5 and 12 and compared with typical levels for children of the same age, sex, and height; blood pressure was considered high if it fell within the top 10 percent of the distribution.

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

What happens next?

More research could help investigators better understand why exposure to nitrogen dioxide during pregnancy was linked to lower, rather than higher, blood pressure in children. This could include exploring possible biological explanations and looking at whether other environmental exposures that occur alongside air pollution may be influencing this finding, such as transportation noise exposure.

Where can I learn more?

Access the full journal article, titled “Pre- and Postnatal Exposure to PM_2.5 and NO₂ and Blood Pressure in Children: Results from the ECHO Cohort,” in Environmental Research.

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

Published December 23, 2025

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Higher Early-Life PM_2.5 Linked to Higher Childhood Blood Pressure, While Prenatal NO₂ Exposure Associated with Lower Blood Pressure, ECHO Study Finds

ECHO Study Finds Association Between Exposure to Certain PFAS and Maternal Depression & Stress During/After Pregnancy

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ECHO Study Finds Association Between Exposure to Certain PFAS and Maternal Depression & Stress During/After Pregnancy

Authors: Susanna D. Mitro, Lyndsay Avalos, 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?

Per- and polyfluoroalkyl substances (PFAS) are a large, complex group of synthetic chemicals found in some household products such as cookware and stain-resistant fabrics. These substances are often referred to as “forever chemicals” because they don’t break down easily, causing them to build up over time in water, soil, and air. Previous studies have shown that PFAS can negatively affect the brain, and there is conflicting evidence about their potential effects on depression and perceived stress during and after pregnancy. Depression and stress during these periods are common and linked to adverse health outcomes for both parents and children. This study aimed to clarify whether PFAS exposure during pregnancy is associated with an increased risk of depression and stress, and whether social factors affect these associations.

What were the study results?

Of the seven PFAS included in this study, some types were linked to changes in depression and stress for pregnant and postpartum participants. For example, higher levels of N-methyl perfluorooctane sulfonamido acetic acid (N-MeFOSAA) were associated with slightly higher depressive symptoms and perceived stress, especially postpartum, while higher perfluorodecanoic acid (PFDA) levels were associated with a lower risk of diagnosed depression and lower prenatal perceived stress. Exposure to perfluorooctanesolfonic acid (PFOS) showed a mixed pattern where moderate exposure was associated with increased depression risk, but the highest exposure was associated with lower depression risk.

When looking at all seven PFAS types as a group, there was generally no strong link to depression diagnosis or severity, but the data did show higher stress at low to moderate exposures, but lower stress as high exposure. The effects of PFAS were different depending on social factors. For example, people who were not born in the U.S. or who had higher social vulnerability sometimes showed stronger links between PFAS and depression or stress.

What was this study's impact?

Overall, the associations observed in this study were small, so more research is needed to fully understand the effects of PFAS on pregnancy mental health. This study adds to mounting evidence that PFAS exposure during pregnancy may have negative health effects during pregnancy, reinforcing the importance of minimizing exposure to PFAS during this sensitive time.

Who was involved?

The study included 4,403 pregnant participants from 16 ECHO Cohort study sites.

What happened during the study?

Researchers measured the levels of seven PFAS in the mother’s blood during pregnancy. Pregnant participants reported whether they received a diagnosis of depression during pregnancy and filled out surveys on their depression and stress symptoms before and after giving birth. The researchers then used statistical methods to evaluate potential associations between PFAS exposure and mental health outcomes and how social factors may have influenced these associations.

What happens next?

Future studies could help researchers clarify the biological mechanisms linking PFAS exposure to depression and stress and explore the role of social factors in influencing these associations.

Where can I learn more?

Access the full journal article, titled “Gestational PFAS concentrations in association with maternal depression and perceived stress during pregnancy and postpartum in the ECHO cohort,” in Environmental Research.

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

Published December 1, 2025

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ECHO Study Finds Association Between Exposure to Certain PFAS and Maternal Depression & Stress During/After Pregnancy

Exposure to Fine Particulate Air Pollution in Early Pregnancy Linked to Lower Birth Weight, ECHO Study Finds

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Exposure to Fine Particulate Air Pollution in Early Pregnancy Linked to Lower Birth Weight, ECHO Study Finds

Authors: Whitney Cowell, 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?

Babies born with low birth weight are at a higher risk for health problems both at birth and later in life. Prior research has shown that exposure to fine particulate matter (PM_2.5)—very small inhalable particles found in air pollution—during pregnancy can negatively affect birth weight. Many past studies examined average exposure over pregnancy, which may miss specific windows when the baby is most sensitive. The goal of this study was to identify the specific weeks in pregnancy when babies are most vulnerable to PM_2.5 exposure.

What were the study results?

Exposure to PM_2.5 during pregnancy was associated with lower birth weight for gestational age, particularly when exposure occurred in the early weeks of pregnancy (weeks 1–5). Male newborns appeared more sensitive to exposure than females. The study also found regional differences, with stronger associations observed in the Northeast, South, and Midwest. This may relate to differences in the types of particles found in the air in these regions.

What was this study's impact?

This study gives us a clearer picture of when during pregnancy air pollution may be most harmful to a baby’s growth. Understanding these sensitive time periods can inform future research on what’s happening in the body during those weeks and why pollution may have a bigger impact during those times.

Who was involved?

The study included 16,868 pregnant participants from the ECHO Cohort, spanning 50 sites across the United States.

What happened during the study?

Researchers applied computer models to estimate pregnant participants' weekly exposure to PM_2.5 throughout their pregnancies. Birth weight was recorded at the time of delivery and then standardized using national growth charts to account for variations in gestational age (length of pregnancy). Analysts used statistical methods to identify how overall and week-specific PM_2.5exposure related to birthweight. These methods also tested whether the impact of PM_2.5differed by the baby’s sex, race or ethnicity of the parents, or the region of the country the mother lived in during pregnancy.

What happens next?

Future studies could help explain how different types and sizes of pollution particles affect baby’s growth. Additional research could also help identify the periods of pregnancy when reducing exposure would have the greatest impact.

Where can I learn more?

Access the full journal article, titled “PM_2.5 in relation to birth weight: exploring windows of susceptibility in the ECHO Cohort,” in JAMA Network Open.

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

Published December 1, 2025

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Exposure to Fine Particulate Air Pollution in Early Pregnancy Linked to Lower Birth Weight, ECHO Study Finds

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 (PM_2.5) 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 PM_2.5. 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 PM_2.5, 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.

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

PFAS Exposure During Pregnancy Not Associated with Behavior Issues in Children, ECHO Study Finds

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PFAS Exposure During Pregnancy Not Associated with Behavior Issues in Children, ECHO Study Finds

Author(s): Catherine Bulka, Rebecca Fry, 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?

Per- and polyfluoroalkyl substances (PFAS) are a class of thousands of man-made chemicals used in some consumer and industrial products like cookware, stain-resistant fabrics, and foams used to fight fires. These substances are often referred to as “forever chemicals” because they don’t break down easily, causing them to build up in water, soil, and air. Previous findings on the effects of prenatal PFAS exposure on child behavior have been inconclusive due to small sample sizes, limited exposure variability, and differing measures of child behavior. This study looked at the relationship between PFAS exposure during pregnancy and child behavior using harmonized measurements collected from many mother-child pairs from across the United States.

What were the study results?

Most of the PFAS detected in pregnant mothers were not clearly linked to behavior problems in their children overall. Children whose mothers had medium levels of exposure to perfluorohexane sulfonate (PFHxS) during pregnancy showed more emotional problems, like being easily upset or withdrawn, especially when they were preschoolers. However, this pattern was not seen at very high or low levels of PFHxS exposure. There were no strong connections between PFAS exposure before birth and behavior problems when the children were older (school-age). Looking at combined exposures to multiple PFAS also did not show any clear relationship with child behavior.

What was the study's impact?

While most PFAS showed no association with behavioral problems, some suggestive, non-linear relationships emerged, indicating that these exposures may influence brain development in complex and unexpected ways. Overall, the study did not find strong or steady links between PFAS exposure during pregnancy and child behavior problems. More research may be needed, especially about newer PFAS replacement chemicals and exposures that happen after birth.

Who was involved?

The study included children from nine ECHO Cohort study sites across the U.S., including 1,723 preschool-age children (1.9-5.9 years) and 627 school-age children (6-15 years).

What happened during the study?

During the study, researchers measured PFAS levels in blood samples collected from mothers between 2- and 42-weeks’ gestation. Later, the researchers assessed children’s behavior using the Child Behavior Checklist (CBCL) when they were preschool- or school-aged. They then used statistical methods to evaluate potential associations between prenatal exposure to PFAS and PFAS mixtures and child behavioral problems.

What happens next?

Future studies could help researchers assess the effects of PFAS exposures during the postnatal period, which may be a more relevant window for childhood brain development and behavioral issues. Additionally, as some PFAS are being phased out of consumer products and replacements are emerging, future studies could help researchers understand the potential effects of exposures to these newer replacement chemicals.

Where can I learn more?

Access the full journal article, titled “Prenatal Exposure to Per- and Polyfluoroalkyl Substances: Association with Child Behavior in the Environmental influences on Child Health Outcomes (ECHO) Cohort,” in Environment International.

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, 2025

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PFAS Exposure During Pregnancy Not Associated with Behavior Issues in Children, ECHO Study Finds

PFAS Exposure Associated with Changes in Gut Microbiome During Pregnancy

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PFAS Exposure Associated with Changes in Gut Microbiome During Pregnancy

Authors: Michael Petriello, 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?

Per- and polyfluoroalkyl substances (PFAS) are a class of thousands of man-made chemicals that are used in various industrial processes and consumer products, including cookware, stain-resistant fabrics, and foams used to fight fires. PFAS can also build up in the environment, contaminating water, food, and air. Because PFAS can last a long time without breaking down, these chemicals can also build up in biological tissues, including the gut lining. PFAS exposure has previously been linked to diseases of the cardiovascular, immune, endocrine, reproductive, and metabolic systems.

Recent studies have shown that PFAS exposure may affect a person’s gut microbiome, the ecosystem of bacteria and other microbes that live in the gut. The composition of the gut microbiome is dependent on a variety of factors, including diet, lifestyle, and exposure to environmental chemicals. These microbes often help aid digestion, support immune health, or protect against pathogens. Changes in the maternal microbiome may impact multiple pregnancy health outcomes related to metabolism and inflammation. Therefore, it is important to identify environmental factors that may affect microbiome health during pregnancy.

What were the study results?

In both sites, prenatal PFAS exposure did not have a significant effect on the diversity of microbes in the maternal gut microbiome. However, the study found there was a significant association between prenatal PFAS exposure and the relative abundance of specific types of bacteria in the maternal gut microbiome. Associations between PFAS exposure and gut microbiome varied by study site, with certain types of bacteria being site-specific and not shared between the Michigan and Atlanta sites.

What was this study's impact?

The effect of PFAS exposure on maternal gut microbiome composition may have broader implications for the health of both the mother and baby. Decreasing exposure to pollutants such as PFAS can improve health outcomes, but complimentary interventions focused on improving microbiome health and resiliency may also help to combat the health effects of environmental chemicals.

Who was involved?

The study included 162 pregnant participants from ECHO study sites in Atlanta and Michigan. The Michigan site (Michigan Archive for Research on Child Health Cohort) included 61 predominantly non-Hispanic White (90.2%) participants. The Atlanta site (Atlanta African American Maternal Child Cohort) included 101 participants who self-identified as Black or African American (100%).

What happened during the study?

Researchers measured PFAS exposure during early or late pregnancy. Later in pregnancy, researchers collected microbiome samples from the mother’s stool to evaluate the types of bacteria present and the bacterial diversity. Statistical methods were used to understand the relationship between PFAS exposure and microbiome composition and diversity.

What happens next?

Future studies could help researchers understand how these microbiome changes are related to maternal and child health outcomes.

Where can I learn more?

Access the full journal article, titled “Prenatal PFAS exposure and outcomes related to microbiome composition and diversity in later pregnancy,” in Environmental Research.

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

Published August 15, 2025

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PFAS Exposure Associated with Changes in Gut Microbiome During Pregnancy