One of the largest investigations ever conducted into chemical exposure during pregnancy has found that expectant mothers regularly encounter dozens of chemicals found in everyday life. The researchers said many of these substances may influence how early a baby is born and how much the infant weighs at birth, both of which can affect health well beyond infancy.
The study of pregnancy urine samples, led by researchers at the UNC Gillings School of Global Public Health, Stanford University School of Medicine, and the Woods Institute for the Environment, was published in JAMA Network Open.
The scientists discovered that participants were exposed to an average of 45 different chemicals, which included phthalates, replacement plasticisers, polycyclic aromatic hydrocarbons (PAHs), and halogenated phenols. These can be found in food, drinking water, air pollution, personal care products, fragrances, and a variety of household items.
“These chemicals are difficult to avoid because they’re found in a wide range of products we use daily. It can be difficult to know whether products contain them, and even when we do know, we have limited control over exposures,” said first author Jessie Buckley, PhD, Professor of Epidemiology at the Gillings School.
“Although there are some practical steps people can take, reducing harmful chemicals at the source is the most effective way to protect children and families.”
Replacement chemicals remain widespread
Phthalates and replacement plasticisers, which were among those identified in the study, are commonly used in products designed for babies and children, including toys, diaper creams, shampoos and other consumer goods.
In 2017, the United States Consumer Product Safety Commission permanently banned or significantly restricted eight commonly used phthalates in children’s toys and products. However, those restrictions did not cover many other products that may be used during pregnancy.
The new research detected several phthalates in participants’ samples, including some that have been introduced as replacements for previously restricted chemicals. The researchers also found a range of plasticiser compounds in the urine samples collected during the study.
More than 5 000 mother-child pairs studied
The analysis included data from more than 5 000 mothers and their children born between 2000 and 2021. Researchers measured chemicals in maternal urine samples and compared those findings with pregnancy duration and birth weight.
The team tested for 113 chemicals commonly present in homes and in air, food, and water.
On average, each sample contained 45 chemicals, while the highest number detected in a single sample was 64. Researchers then evaluated how these exposures were associated with differences in gestational age and birth weight.
Several phthalates and alternative plasticisers were consistently associated with shorter pregnancies. Phthalates, replacement plasticisers, and PAHs were also linked to lower birth weight. In addition, some lesser studied chemicals identified in the research, including halogenated phenols, showed associations with lower birth weight.
The researchers also detected newer plasticisers that were introduced as alternatives to more widely recognised toxic chemicals such as phthalates. However, they found that these replacement chemicals appeared to have health effects similar to the substances they were intended to replace.
Call for stronger safety policies
“Our study highlights the need for stronger policies to protect people from toxic chemicals,” said senior researcher Tracey Woodruff, PhD, Professor of Epidemiology and Population Health at Stanford.
“For example, we found that several newer chemicals used to replace toxic ones are also harmful, which underscores why new and replacement chemicals must be properly evaluated before they are put on the market. Further, government agencies that evaluate health risks for toxic chemicals like phthalates should incorporate our findings to reduce exposures and ensure healthier pregnancies.”
Buckley said the findings add to a growing body of evidence showing the importance of limiting chemical exposures during pregnancy.
“They underscore the importance of reducing chemical exposures affecting pregnancy, as even small changes in birthweight or gestational age can have significant impacts on children’s health.”
Woodruff said many sources of exposure are difficult for individuals to control on their own.
“Pregnant women are at risk of chemical exposure through multiple sources, many of them beyond their control,” she said. “Governments and companies need to do a better job of reducing harmful chemicals in everyday products and ensuring new chemicals are safe, which will lead to healthier children and families.”
The research was supported by the Environmental influences on Child Health Outcomes (ECHO) Programme, Office of the Director, National Institutes of Health.
Study details
Gestational exposure to 10 classes of priority chemicals and birth outcomes in the ECHO Cohort
Jessie Buckley, Diana Pacyga, Xiaoshuang Xun et al.
Published in JAMA Network on 17 June 2026
Abstract
Importance
Gestational environmental chemical exposures are widespread. Some chemicals are known to adversely affect birth outcomes, but many remain understudied.
Objective
To evaluate associations of gestational exposure to a priori identified chemicals in 10 classes with birth outcomes in a large, diverse US cohort.
Design, Setting, and Participants
In the prospective Environmental influences on Child Health Outcomes Cohort study, 5318 mother-child pairs were enrolled from January 1, 2000, to December 31, 2021, with data on gestational urinary chemical concentrations, gestational age at birth, and birth weight. Statistical analysis was performed from January 2024 to February 2026.
Exposures
In single, midgestation (median, 25 weeks [IQR, 21-30 weeks]) urine samples, concentrations of 113 analytes (chemicals or their metabolites) from 10 chemical classes were simultaneously measured: fungicides and herbicides (n = 11), insecticides (n = 20), halogenated phenols (n = 5), organophosphate esters (n = 10), benzophenones (n = 6), bisphenols (n = 14), parabens (n = 6), antimicrobials (n = 2), phthalates or alternative plasticizers (n = 32), and polycyclic aromatic hydrocarbons (PAHs) (n = 7).
Main Outcomes and Measures
Linear mixed-effects regression models with a random effect for site were used to estimate covariate-adjusted differences in gestational age at birth (days) and birth weight-for-gestational age (BW-GA) z scores per IQR increase in urinary analyte concentrations. In secondary analyses, odds ratios (ORs) for preterm birth and small for gestational age (SGA) were estimated.
Results
In the sample of 5318 mother-child pairs, most infants (2667 female [50%]; median gestational age at birth, 39.0 weeks [IQR, 38.0-40.0 weeks]) were born to college-educated (67% [3218 of 4785]), parous (56% [2815 of 5007]) mothers (median age at delivery, 30.7 years [IQR, 26.1-34.3 years]). A total of 43 of 113 analytes (38%) were detected in 50% or more of samples. Multiple phthalates or alternative plasticisers were associated with younger gestational age at birth or lower BW-GA z scores; for example, summed diisononyl phthalate metabolites were associated with a 0.6-day (95% CI, −1.0 to −0.1 days) younger gestational age (preterm birth OR, 1.16 [95% CI, 1.01-1.34]), and summed phthalate or alternative plasticisers were associated with a 0.06 (95% CI, −0.11 to −0.02) lower BW-GA z score (SGA OR, 1.09 [95% CI, 0.93-1.27]). Two halogenated phenols, benzophenone 8, bisphenol F, and several PAHs were associated with lower BW-GA z scores; for example, 1- and 9-hydroxphenanthrene were associated with a 0.04 (95% CI, −0.08 to −0.01) lower BW-GA z score (SGA OR, 1.13 [95% CI, 1.01-1.27]).
Conclusions and Relevance
This large cohort study of diverse US pregnancies found widespread exposure to 10 classes of environmental chemicals, many of which were associated with differences in gestational age at birth or lower BW-GA z scores. These findings indicate that reducing gestational exposure to chemicals, particularly phthalates or alternative plasticisers and PAHs, could promote healthy deliveries and better child outcomes.
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