Fish But Not Supplements Consumed in Pregnancy Associated With Lower Rates of Autism Diagnosis And Related Traits, ECHO Cohort Study Finds

Authors: Emily Oken, Kristen Lyall, 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?

Fish consumption during pregnancy provides an important source of omega-3 fatty acids, an essential nutrient for supporting child health and neurodevelopment. However, in the U.S., people who are pregnant or can become pregnant are not eating enough fish or get enough omega-3 fatty acids through diet or supplements. Few studies have explored prenatal fish consumption and supplement use in association with autism spectrum disorder (ASD) diagnosis or autism-related traits. This study aims to investigate the relationship between fish consumption or omega-3 supplement use and an ASD diagnosis or the presence of autism-related traits.

What were the study results?

Fish consumption during pregnancy was associated with a 20% lower likelihood of ASD diagnosis and fewer autism-related traits in offspring. The associations were somewhat stronger for female offspring. Taking fish oil supplements containing omega-3 fatty acids during pregnancy was not associated with an ASD diagnosis or autism-related traits. However, supplement use was associated with a slight increase in scores on the Social Responsiveness Scale (SRS), a widely used survey completed by parents or caregivers to report on their child’s possible autism-related traits.

What was the study's impact?

These findings are consistent with current dietary guidelines that support fish intake during pregnancy and support continued public health efforts to encourage fish intake.

Who was involved?

The participants were children born between 1999 and 2019 and their parents at three of the Environmental influences on Child Health Outcomes (ECHO) Cohort research sites. The sites selected from samples considered a higher likelihood for autism, either due to family history or preterm birth.

What happened during the study?

The researchers studied the relationship between maternal fish intake and omega-3/fish oil supplement use during pregnancy and the occurrence of clinician-diagnosed autism and parent-reported autism-related traits. These traits were measured using the Social Responsiveness Scale (SRS), a widely used survey completed by parents or caregivers. Fish consumption and supplement use were assessed based on self-reported dietary information from participants.

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?

Future research could examine how chemical contaminants found in some fish could potentially influence child health and development. Additional studies could look at the relationship between self-reported data on fish consumption and supplement use during pregnancy, biological markers of fish consumption, and child health outcomes. Combining biological data and self-reported data could provide a more complete picture of the overall benefits of fish consumption during pregnancy.

Where can I learn more?

Access the full journal article titled “Association of Maternal Fish Consumption and Omega-3 Supplement Use During Pregnancy with Child Autism-Related Outcomes: Results from a Cohort Consortium Analysis” in the American Journal of Clinical Nutrition.

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

Published September 2024

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Fish But Not Supplements Consumed in Pregnancy Associated With Lower Rates of Autism Diagnosis And Related Traits, ECHO Cohort Study Finds

Eating Fish But Not Omega-3 Supplements During Pregnancy Associated With Lower Likelihood Of Autism Diagnosis, NIH-Funded Study Finds

Posted on September 3, 2024August 27, 2025 by Jodi Snare

FOR IMMEDIATE RELEASE

Eating any amount of fish during pregnancy was associated with about a 20% lower likelihood of autism spectrum disorder (ASD) diagnosis, particularly in females, and a slight reduction in autism-related traits in offspring, according to a new study funded by the Environmental influences on Child Health Outcomes (ECHO) Program at the National Institutes of Health.

However, researchers did not find the same association with supplements containing omega-3 fatty acids.

Fish is an important source of omega-3 fatty acids, an essential nutrient during pregnancy for supporting maternal health and child neurodevelopment. A recent analysis of ECHO Cohort data revealed that about 25% of the pregnant participants reported never eating fish or consuming it less than once a month during their pregnancy. Even fewer participants reported taking omega-3 fish oil supplements.

ECHO Cohort researchers wanted to see whether low fish consumption and omega-3 supplement use during pregnancy might be associated with the occurrence of an autism diagnosis or parent-reported autism-related traits.

“Our study contributes to a growing body of evidence that demonstrates the role that prenatal diet can play in autism-related outcomes in offspring,” said ECHO Cohort researcher Emily Oken, MD, MPH, of Harvard Medical School.

Dr. Oken said the findings underscored the need for better public health messaging about guidelines for fish consumption for pregnant women, considering the low fish intake in the U.S. and the rising diagnoses of autism.

What happened during the study?

Researchers analyzed data from about 4,000 participants, examining the relationships among fish intake, supplement use, and neurodevelopmental outcomes related to autism.

Fish consumption and omega-3 supplement use were measured with dietary information reported by participants. Participants’ fish consumption was categorized as less than once a month, more than once a month but less than weekly, weekly, and two or more servings per week. About 20% of adult participants reported no fish intake, and most reported not using omega-3 or fish oil supplements.

The researchers then looked at the relationship between maternal fish intake and omega-3 fish oil supplement use during pregnancy and the occurrence of clinician-diagnosed autism and parent-reported autism-related traits. These traits were measured using the Social Responsiveness Scale (SRS), a widely used survey completed by parents or caregivers. Higher scores on the SRS indicate the presence of more autism-related behaviors.

Consuming fish during pregnancy was associated with a lower likelihood of offspring being diagnosed with autism and a slight decrease in total SRS scores compared to not eating fish. These results were consistent across all levels of fish consumption, from "any" amount or "less than once per week" to "more than twice per week." No significant associations were found between omega-3 fish oil supplements and autism diagnosis compared to no use.

Experts recommend that people consume additional omega-3 fatty acids during pregnancy. Prenatal fish intake is a key source of omega-3 fatty acids that are critical for fetal brain development. However, fish and omega-3 fatty acid supplementation in the U.S. is low.

“This study provides yet more evidence for the safety and benefit of regular fish consumption during pregnancy,” said Dr. Oken. “Other proven benefits include lower risk for preterm birth and improved cognitive development.”

Dr. Oken led this collaborative research published in the American Journal of Clinical Nutrition.

Oken, E. & Lyall, K. (2024) Association of maternal fish consumption and ω-3 supplement use during pregnancy with child autism-related outcomes: results from a cohort consortium analysis. American Journal of Clinical Nutrition. 10.1016/j.ajcnut.2024.06.013

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About ECHO: Launched in 2016, the Environmental influences on Child Health Outcomes (ECHO) Program is a research program in the Office of the Director at the NIH with the mission to enhance the health of children for generations to come. ECHO investigators study the effects of a broad range of early environmental influences on child health and development. For more information, visit echochildren.org.

About the NIH: NIH, the nation’s medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information, visit www.nih.gov.

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ECHO Cohort Study Finds Association Between PFAS and Bioactive Lipids

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ECHO Cohort Study Finds Association Between PFAS and Bioactive Lipids

Authors: Himal Suthar, Max Aung, 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 that have been used in consumer products around the world since about the 1950s. They are ingredients in various everyday products. For example, PFAS are used to keep food from sticking to packaging or cookware, make clothes and carpets resistant to stains, and create firefighting foam that is more effective. People are most likely exposed to these chemicals by consuming PFAS-contaminated water or food, using products made with PFAS, or breathing air containing PFAS.

Because PFAS break down slowly, if at all, people and animals are repeatedly exposed to them, and blood levels of some PFAS can build up over time. Scientific studies have identified multiple health effects associated with PFAS exposure.[1] Women exposed to PFAS during pregnancy are at increased risk for adverse birth outcomes and pregnancy complications.

Lipids are fatty molecules that perform a variety of functions in the body—from forming the membranes of cells to serving as a building block for certain hormones. Changes in bioactive lipids—broadly defined as a category of lipids with signaling properties that cause biological effects and changes in the body—have been linked to PFAS exposure and adverse pregnancy outcomes. This study aimed to compare the concentration of PFAS in the blood of pregnant participants with levels of bioactive lipids in three important metabolic pathways.

[1] National Institute of Environmental Health Sciences: Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) (nih.gov)

What were the study results?

The research team analyzed the associations between 12 types of PFAS, in pairs and as mixtures, and 50 bioactive lipids in blood plasma in pregnant participants across three ECHO Cohort Study Sites. When researchers looked at data from different study sites, they found that higher levels of PFAS in blood were often linked with higher levels of certain bioactive lipids. The research team also noticed differences in the distribution of bioactive lipid compounds between individual study sites, possibly driven by variations in the genetic makeup and sociodemographic characteristics of the populations or differences in environmental exposures due to diet.

Footnote: Results reported here are for a single study and reflect an observed correlation. 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 this study's impact?

The similarity of results researchers found from the analysis of mixtures of PFAS chemicals and individual PFAS chemicals indicate that specific bioactive lipids could be useful biomarkers of PFAS exposure. Biomarkers are biological indicators of a particular health effect or status – in this case, PFAS exposure. They can be found in blood, urine, or other body fluids and can be substances, characteristics, genes, or proteins. This insight could help in understanding and addressing the health effects of PFAS by expanding screening methods.

The bioactive lipids measured in this study have not yet been tested as routine biomarkers in clinical settings. However, these findings aid in advancing the future of healthcare as additional and more complex lipid biomarkers become measurable and are tested for clinical use.

These findings encourage researchers to prioritize the study of PFAS and bioactive lipids pairs in future testing in addition to individually studying the effect of different types of PFAS. Additionally, this study highlights the importance of regulating the 12 types of PFAS observed.

Who was involved?

This study included 414 pregnant participants from three ECHO Cohort study sites: Chemicals in Our Bodies based in San Francisco, ECHO-PROTECT based in Puerto Rico, and Illinois Kids Development Study based in Chicago.

What happened during the study?

The research team estimated associations between prenatal PFAS exposure and bioactive lipids, measuring the levels of 12 types of PFAS and 50 bioactive lipids in 414 pregnant participants. Researchers quantified associations by using various statistical analyses while controlling for several factors (e.g., maternal age, gestational age at sample collection, maternal education, pre-pregnancy BMI).

What happens next?

The researchers plan to measure associations between bioactive lipids and peri- and prenatal mental health outcomes including perinatal and postpartum depression. Future studies could also look at the influence of other variables on this relationship. For example, researchers could investigate the influence of diet, which has been linked to changes in both PFAS and bioactive lipid concentrations.

Where can I learn more?

Access the full journal article, titled “Cross-Sectional Associations between Prenatal Per- and Poly-Fluoroalkyl Substances and Bioactive Lipids in Three Environmental Influences on Child Health Outcomes (ECHO) Cohorts,” in Environmental Science and Technology.

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

Published May 14, 2024

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ECHO Cohort Study Finds Association Between PFAS and Bioactive Lipids

ECHO Study Investigates Relationship Between Phthalate Exposure and High Blood Pressure, Related Complications During Pregnancy

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ECHO Study Investigates Relationship Between Phthalate Exposure and High Blood Pressure, Related Complications During Pregnancy

Authors: John Meeker, Jordan Kuiper, 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?

High blood pressure during pregnancy, which can develop into the more serious conditions of preeclampsia* or eclampsia*, can pose significant health risks to pregnant women and their children. Potential environmental risk factors for ongoing high blood pressure during pregnancy and more severe pregnancy complications like preeclampsia or eclampsia have not been well-studied. Phthalates are chemicals used in various products, including plastics, personal care products, and food packaging. There is evidence, though limited, that exposure to some phthalates may be associated with preeclampsia and ongoing high blood pressure during pregnancy.

*Preeclampsia and eclampsia are pregnancy-related high blood pressure disorders. In preeclampsia, the mother’s high blood pressure reduces the blood supply to the fetus, which may get less oxygen and fewer nutrients. Eclampsia is when pregnant women with preeclampsia develop seizures or coma.

Link to source

What were the study results?

The researchers evaluated phthalate exposure by measuring urine levels of certain metabolites, which are small molecules the body makes when it breaks down foods, drugs, chemicals, or its own tissues (for example, fat or muscle tissue). This study found that higher levels of these metabolites were associated with a higher risk of developing preeclampsia, eclampsia, and/or ongoing high blood pressure during pregnancy. For example, a doubling of mono (3-carboxypropyl) phthalate (MCPP)—a metabolite linked to phthalates found in PVC-based plastics and insect repellents—was associated with 12% increased risk of developing preeclampsia or eclampsia.

For combined exposures, researchers divided participants into four groups, or quartiles, by increasing level of exposure. A quartile increase in the combined phthalate mixture was associated with a 27% increased risk of preeclampsia or eclampsia. This effect was generally larger among pregnant participants carrying female fetuses.

What was this study's impact?

The findings of this study suggest that exposure to certain phthalates found in plastics and other consumer products may be associated with pregnancy complications like gestational hypertension or preeclampsia.

Who was involved?

The study included data from 3,430 participants from eight ECHO sites across the U.S. which enrolled pregnant participants from 1999 to 2019.

What happened during the study?

The researchers measured the levels of 13 metabolites linked to phthalate exposure in urine samples collected at least once during pregnancy. They then evaluated the association between individual phthalates, as well as the combined mixture of phthalates, with the risk of developing preeclampsia, eclampsia, or ongoing high blood pressure during pregnancy.

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?

Additional well-designed studies are needed to better understand the association between phthalate exposure and high blood pressure during pregnancy, the underlying biological mechanisms, and effective interventions that could reduce the risk of these kinds of pregnancy complications.

Where can I learn more?

Access the full journal article, titled “Urinary concentrations of phthalate metabolites in relation to preeclampsia and other hypertensive disorders of pregnancy in the Environmental influences on Child Health Outcomes (ECHO) program,” 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 May, 2024

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ECHO Study Investigates Relationship Between Phthalate Exposure and High Blood Pressure, Related Complications During Pregnancy

Study Finds Link Between Phthalate Exposure During Pregnancy and Development of Multiple Health Outcomes in Children

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Study Finds Link Between Phthalate Exposure During Pregnancy and Development of Multiple Health Outcomes in Children

Authors: Drew Day, Kaja Z. LeWinn, 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?

Chronic health conditions, such as asthma and obesity, can develop together during childhood but are usually studied separately. ECHO researchers used new machine learning tools to explore patterns of health outcomes in children and then looked at how common exposures are associated with multiple health conditions.

The goal of this study was to use data from ECHO Cohort research sites across six U.S. cities to characterize “clusters,” or patterns of obesity-related, lung health, and brain development outcomes in children and to investigate how these patterns relate to mothers’ exposures to chemicals called phthalates during pregnancy. Phthalates are chemicals widely used in plastics, and maternal exposure to certain phthalates have been linked to preterm birth.

What were the study results?

The researchers identified three groups of children with a pattern of health outcomes that occurred together:

A group of relatively healthy children;
A group of children with lower IQ, elevated obesity,
and slightly elevated asthma-related outcomes such as asthma, wheezing, and allergies; and
Another group of children with high asthma-related outcomes along with elevated obesity and some increase in anxiety- and depression-related outcomes.

Compared to children in the healthy group, other groups had more male children, mothers with higher BMI and lower education attainment, and lower household incomes. The researchers found that children—particularly boys—were more likely to be in the third group if their mothers were exposed to phthalates during pregnancy.

What was this study's impact?

These findings suggest that exposure to phthalates during pregnancy might be associated with an increased risk of developing not only asthma and related lung outcomes, but also obesity and mental health issues such as anxiety and depression. This study also suggests that low-income households are at higher risk for worse childhood health outcomes.

The three patterns of health outcomes seen in this study also reveal more about how pediatric diseases might arise together, which could help inform future research on what biological processes contribute to those health outcome patterns as well as better treatments and interventions to enhance child health.

Who was involved?

Researchers looked at health outcomes in 1,092 children across six U.S. cities. Researchers were able to collect measurements of phthalate exposure during pregnancy from 856 of these children’s mothers.

What happened during the study?

The researchers measured 15 health outcomes in children between the ages of 4 and 9 years—including body mass index (BMI), IQ, anxiety, depression, irritability, learning disabilities, speech problems, asthma, wheeze, and nasal allergies. The researchers evaluated how children developed multiple outcomes and investigated how the probability of being in a particular group was affected by exposure to 15 plastic-associated phthalate chemicals during pregnancy. The researchers measured phthalate exposure during pregnancy using urine samples collected from 2007–2014 from mothers during late pregnancy.

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?

This study’s multi-outcome approach can be used in future studies to identify public health risks that may affect central biological processes that result in multiple negative health outcomes. ECHO Cohort researchers are working to extend this method to include several additional U.S. research sites, which will allow them to evaluate whether similar patterns are observed in a larger dataset. Larger studies will also help researchers characterize how demographic differences like income and sex may influence the development of multiple health outcomes during childhood.

Where can I learn more?

Find the full research article, titled “Subpopulations of children with multiple chronic health outcomes in relation to chemical exposures in the ECHO-PATHWAYS consortium,” in the journal 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 March, 2024

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Study Finds Link Between Phthalate Exposure During Pregnancy and Development of Multiple Health Outcomes in Children

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

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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.

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?

Previous studies have shown that diet during pregnancy can impact the physical and mental health of the pregnant women. However, less is known about how food insecurity affects health outcomes for newborns. For this study, ECHO researchers analyzed data to understand what connections might exist between where a pregnant woman lives, their access to food, and birth outcomes.

What were the study results?

The study found that living in neighborhoods where residents have lower incomes, limited food access, or limited vehicle access was associated with lower birthweights and an increased risk of babies born small for gestational age. However, researchers didn’t find any association between individual experiences of food insecurity and birth outcomes.

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 was this study's impact?

Given the long-term effects of adverse birth outcomes on later cardiovascular disease risk and other conditions, more research is needed to evaluate whether interventions and policies that improve food access during pregnancy would be effective in improving birth outcomes and promoting child health. A variety of strategies could be effective at improving birth outcomes, including strategies to increase neighborhood food access, improve food affordability in neighborhoods with low food access, or directly provide healthy foods to individuals during pregnancy.

Who was involved?

This study included 22,206 pregnant participants enrolled in 53 ECHO research sites that collected information on neighborhood-level food access data and birth outcomes. Of these participants, 24% lived in a low-income neighborhood where a third or more residents lived over one mile from a grocery store (or more than 10 miles in rural areas). About 14% of the participants in this study lived in neighborhoods with high poverty rates where more than 100 households had no access to a vehicle and lived more than half a mile from the nearest grocery store.

What happened during the study?

To conduct this study, researchers matched pregnant individuals' home addresses with information about nearby food availability from the U.S. Food Access Research Atlas, which provided data on household income, the availability of a household vehicle, and where people can access food in different neighborhoods. Researchers also assessed individual-level food insecurity during pregnancy using the Crisis in Family Systems-Revised questionnaire.

What happens next?

Additional studies are needed to examine how health habits, chemical exposures, and other related factors may also influence birth outcomes.

Where can I learn more?

Access the full journal article, titled “Birth Outcomes in Relation to Neighborhood Food Access and Individual Food Insecurity During Pregnancy in the Environmental influences on Child Health Outcomes (ECHO)-Wide Cohort Study,” in American Journal of Clinical Nutrition.

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, 2024

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

ECHO Study Shows Fish Consumption and Omega-3 Supplement Use Uncommon During Pregnancy

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ECHO Study Shows Fish Consumption and Omega-3 Supplement Use Uncommon During Pregnancy

Authors: Emily Oken, Kristen Lyall, 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?

Omega-3 fatty acids are essential nutrients for supporting positive health outcomes. Getting enough of these nutrients during pregnancy is vital for child health and neurodevelopment and may also improve other pregnancy outcomes. Prior research on the demographic characteristics associated with fish and supplement use during pregnancy has been limited, involving fewer participants and older data that may not represent current intake.

What were the study results?

During the study, about 25% of pregnant participants did not eat any fish or ate it less than once per month. Older participants were more likely to eat fish. Participants who were non-Hispanic Black, non-Hispanic Asian, or Hispanic ate less fish on average when compared to those who identified as non-Hispanic White. Participants categorized as overweight were also less likely to eat fish. Only about 1 in 6 pregnant participants reported taking omega-3 supplements. Supplement use was more common in participants who were older and had more education, had a lower body mass index (BMI), and ate fish.

What was the study's impact?

One-quarter of participants in this large, nationwide study rarely or never consumed fish during pregnancy, and omega-3 supplement use was uncommon, even among those who did not consume fish. Given the role of omega-3 fatty acids in preventing preterm birth and supporting child health and neurodevelopment, experts recommend pregnant women get at least 500 mg of omega-3 fatty acids per day through supplements or consuming fish that is low in mercury.

Learn more about the FDA’s and EPA’s current recommendations for eating fish during pregnancy here.

Who was involved?

This study included 10,800 pregnant participants enrolled in 23 ECHO research sites that collected information on fish consumption and 12,646 participants at 35 ECHO research sites that collected information on omega-3 supplement use. Information on fish consumption and omega-3 supplement use was collected from pregnant participants from 1999 to 2020.

What happened during the study?

The researchers collected information on fish intake during pregnancy and grouped participants based on the frequency of their fish consumption: never or less than once per month, once per month to less than once per week, one to two times per week, or more than twice per week. The researchers also collected information on participants’ omega-3 supplement intake. They then compared participant fish consumption and supplement use information across various demographic and lifestyle characteristics, including age, race, ethnicity, education, weight, and smoking status.

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 diet without first consulting your healthcare professional.

What happens next?

Future research may examine how fish consumption during pregnancy relates to childhood developmental outcomes such as autism-related traits.

Where can I learn more?

Access the full journal article titled “Demographic and health characteristics associated with fish and n-3 fatty acid supplement intake during pregnancy: results from pregnancy cohorts in the ECHO program” in Public Health Nutrition.

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

Published February 27, 2024

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ECHO Study Shows Fish Consumption and Omega-3 Supplement Use Uncommon During Pregnancy

ECHO Study Finds Link Between Phthalate Exposure and Preterm Birth, Estimates Potential Costs

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ECHO Study Finds Link Between Phthalate Exposure and Preterm Birth, Estimates Potential Costs

Authors: Leonardo Trasande, 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?

Phthalates are widely used chemicals found in some consumer products, and previous research has linked phthalate exposure to preterm birth. In response, the use of di-2-ethylhexyl phthalate (DEHP), a common type of phthalate, has decreased in recent years. However, there is limited research on the effects of the replacement phthalates, and the costs associated with phthalate exposure remain unquantified. ECHO Cohort researchers wanted to learn about the potential connections between phthalates, their metabolites in the urine of pregnant individuals, and birth outcomes—including birth weight and length of pregnancy. The study also sought to estimate the potential costs associated with adverse birth outcomes.

What were the study results?

When the researchers grouped mothers based on the amount of DEHP metabolites (substances produced when the body breaks down DEHP) found in their urine, they found that the 10 percent with the highest levels had a 50 percent higher chance of giving birth before the 37th week of pregnancy compared to the 10 percent with the lowest levels.

Some common alternatives to DEHP were associated with even higher risk of preterm birth. Women exposed to the highest amounts of these alternative chemicals—phthalic acid, di-isodecyl phthalate (DIDP), di-n-octyl phthalate (DnOP), and diisononyl phthalate (DiNP)—had twice the risk of preterm birth compared to those with little to no exposure to these alternatives.

Researchers estimated that the number of premature births in the U.S. that could be linked to phthalate exposure in 2018 was between 24,000 and 120,000, potentially costing between $1.6 billion and $8.1 billion in medical expenses over the lifetime of the children.

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 was this study's impact?

This ECHO Cohort research examines the effect of phthalates on birth outcomes such as preterm birth and birth weight. These findings associated adverse birth outcomes with exposure to DEHP and its chemically similar substitutes, which can inform the development of policies, programs, and practices that can help prevent or lessen potentially harmful exposures during pregnancy.

Who was involved?

The study included 5,006 mother-child pairs from 13 ECHO Cohort Study Sites across the U.S. Researchers included individuals with information on up to 20 urinary phthalate metabolites. The pregnant participants were aged 25 to 34 at the time they gave birth.

What happened during the study?

The researchers analyzed levels of 20 phthalate metabolites in urine samples collected at three points during each participant’s pregnancy. They also investigated the differences between specific types of phthalates, comparing DEHP with several newer alternatives developed to replace it. Then, the team looked for associations between these metabolite levels and preterm births. They also calculated the number of premature births that could be linked to phthalate exposure and the possible associated costs over the lifetime of the child.

What happens next?

Future research could look at how exposure to replacement phthalates affects child development after birth. The European Union has prohibited the use of certain phthalates in some consumer products—as have California and a few other U.S. states.

Where can I learn more?

Access the full journal article, titled “Prenatal phthalate exposure and adverse birth outcomes in the USA: a prospective analysis of births and estimates of attributable burden and costs,” in The 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 February, 2024

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ECHO Study Finds Link Between Phthalate Exposure and Preterm Birth, Estimates Potential Costs

ECHO Study Finds Flame-Retardant Chemicals May Increase Risk Of Preterm Birth and Higher Birth Weight

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ECHO Study Finds Flame-Retardant Chemicals May Increase Risk Of Preterm Birth and Higher Birth Weight

Authors: Deborah Bennett, Jiwon Oh, 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?

Manufacturers commonly use flame-retardant chemicals known as organophosphate esters (OPEs) in products such as furniture, baby items, electronics, clothes, and building materials to prevent fires and make plastics more flexible. People can come into contact with OPEs in various ways, including swallowing or breathing indoor dust or absorbing it through the skin. Animal studies have revealed that OPEs can harm the growth and development of offspring. However, the connection between OPE exposure during pregnancy and birth outcomes has been unclear. ECHO researchers wanted to learn if there was a link between OPE levels in the urine of pregnant individuals and specific birth outcomes.

What were the study results?

Pregnant individuals exposed to specific classes of OPEs may face an increased risk of preterm birth, especially for baby girls and babies with higher birth weights. Three of these substances—diphenyl phosphate (DPHP), a combination of dibutyl phosphate and di-isobutyl phosphate (DBUP/DIBP), and bis(1,3-dichloro-2-propyl) phosphate—were associated with shorter pregnancies and higher risks of preterm birth only among female infants. Among male infants, higher concentrations of DPHP were associated with longer pregnancies.

Babies born to mothers with detectable levels of three other OPE markers—bis(1-chloro-2-propyl) phosphate, bis(2-methylphenyl) phosphate, and dipropyl phosphate—tended to have higher birth weights compared to those whose mothers had no detectable levels of these substances.

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 was this study's impact?

In the past decade, OPEs have been increasingly used as flame retardants after polybrominated diphenyl ether (PBDE) flame retardants were phased out due to health risks. ECHO research examines the potential impact of these now more widespread OPE chemicals on pregnancy outcomes such as preterm birth and birth weight. The findings can inform policies, programs, and practices to help decrease exposure.

Who was involved?

The study included 6,646 pregnant participants at 16 ECHO Cohort Study Sites across the U.S. and Puerto Rico.

What happened during the study?

Researchers measured a total of nine OPE markers in urine samples collected from 6,646 pregnant participants across 16 ECHO Cohort Study Sites—often during their third or second trimesters. The researchers then assessed birth outcomes, including the length of pregnancy and birth weight, using medical records or parent reports.

What happens next?

OPEs tend to stay in the human body for short periods, usually hours to days. To better understand how these chemicals might affect birth outcomes, researchers can use multiple measurements of urinary OPE biomarkers. This could help identify when the body might be more sensitive to these chemicals. Additionally, learning more about how people are exposed to these chemicals can help identify ways to reduce exposure, especially during pregnancy.

Where can I learn more?

Access the full journal article, titled “Associations of Organophosphate Ester Flame Retardant Exposures during Pregnancy with Gestational Duration and Fetal Growth: The Environmental influences on Child Health Outcomes (ECHO) Program,” in Environmental Health Perspectives.

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

Published January 24, 2024

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ECHO Study Finds Flame-Retardant Chemicals May Increase Risk Of Preterm Birth and Higher Birth Weight

ECHO Study Suggests Placenta Development for Male, Female Infants May Differ

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ECHO Study Suggests Placenta Development for Male, Female Infants May Differ

Authors: Catherine Bulka, Rebecca Fry, 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.

What were the study results?

This study found that gene activity in the placenta might differ based on the infant’s sex, suggesting that the placentas of males and females develop differently. The placenta is an organ formed during pregnancy to nourish the fetus that goes through many changes during the length of the pregnancy to support the development of the infant.

Previous studies have found that a number of changes occur in the genetic make-up of the placental tissue throughout pregnancy. The current study suggests that some of these genetic changes may differ based on whether the baby is male or female. The researchers looked at gestational age (the amount time the baby spent in-utero) to compare placentas among males and female fetuses at different points in time. Among females, the researchers saw modifications in genes related to the immune system. Among males, there was modifications in genes related to the transport of molecules into the placenta.

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 was the study's impact?

This study identified differences in the location of modifications of placental DNA between male and female infants at different gestational ages. The most prominent differences were linked to genes that play significant roles in immunity, inflammation, and pregnancy complications. These differences seen between male and female infants may be important when looking at sex-specific health and developmental outcomes.

Why was this study needed?

The placenta is crucial for fetal growth and development. No previous study had considered the role of infant sex in placental development, despite accumulating evidence that females and males develop differently in utero.

Who was involved?

This study included 774 infants from 4 ECHO research sites. In total, the study included 355 female and 419 male infants. One of the research sites enrolled infants born at less than 28 weeks, which provided samples from the earliest viable births.

What happened during the study?

Research sites compared the placental tissue of male and female infants to determine associations between gestational age and modifications of placental DNA. Researchers then located the modifications and identified the closest genes, allowing them to analyze the biological significance of the modifications.

What happens next?

Researchers are now using this data to estimate an infant’s “biological” rather than “chronological” gestational age based on the modification of placental DNA. The findings of this study suggest that it may be important to consider the infant’s sex when calculating “biological” gestational age.

Where can I learn more?

Access the full journal article, titled “Sex-based differences in placental DNA methylation profiles related to gestational age: an NIH ECHO meta-analysis,” in Epigenetics.

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

Published December 2023

Access the associated article.

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ECHO Study Suggests Placenta Development for Male, Female Infants May Differ