Exposure to certain chemicals during pregnancy was linked to differences in gestational age and birthweight, highlighting the need to better understand the potential health effects of both well-known and less-studied chemical exposures, according to a recent ECHO Cohort study led by Jessie Buckley, PhD, MPH of UNC Chapel Hill and Tracey Woodruff, PhD, MPH of Stanford University.

Pregnant women in the United States may be exposed to dozens of chemicals at the same time, including some that are not well understood.

“We found exposures to several newer chemicals that have been used to replace toxic ones. These chemicals are not well-studied but we found that they can have similar health effects as the chemicals they replace,” said Dr. Woodruff. “This finding underscores the need to better track and evaluate new chemicals before they are introduced.”

Researchers analyzed urine samples collected from pregnant participants and detected an average of 45 chemicals out of 113 measured. The study focused on whether higher levels of these chemicals were associated with differences in birth outcomes, including gestational age, birthweight adjusted for gestational age, and risk of preterm birth or being born smaller than expected.

Key findings include:

• Exposure to several types of chemicals was associated with differences in birth outcomes.
• Certain phthalates (used in plastics) and polycyclic aromatic hydrocarbons (found in air pollution and some foods) were linked to shorter pregnancies or lower birthweight for gestational age.
• Some less-studied chemicals, such as halogenated phenols, were also associated with lower birthweight for gestational age.
• In contrast, higher levels of some insecticides and benzophenones were associated with longer gestational age or higher birthweight for gestational age.

The study included 5,318 mother–child pairs from 18 ECHO Cohort sites across the United States, with participants enrolled between 2000 and 2021. Researchers accounted for factors that can influence birth outcomes—such as maternal age, education, and tobacco use during pregnancy—to better isolate the associations between chemical exposure and outcomes.

While the observed differences in birth outcomes were small, the findings underscore how widespread chemical exposures are during pregnancy and the importance of continuing to evaluate their potential health effects.

“Our findings add to existing evidence that chemical exposures during pregnancy can worsen birth outcomes, highlighting the importance of reducing toxic chemical exposures during early life,” said Dr. Buckley.

Future research could explore whether these exposures are also linked to other child health outcomes, such as neurodevelopment, obesity, or asthma.

This collaborative research, titled “Gestational exposure to ten classes of priority chemicals and birth outcomes in the ECHO Cohort,” was published in JAMA Network Open.