A growing body of research suggests that environmental chemicals and psychosocial stressors influence pregnancy outcomes. Now, a major U.S. study has revealed that their combined effects may be more consequential than previously understood. Drawing on data from the Environmental influences on Child Health Outcomes (ECHO) Program, researchers found that the detrimental effects of certain chemicals on birth outcomes were amplified when the mother experienced high levels of psychosocial stressors (e.g., anxiety, depression, perceived stress, and early-life trauma).

Researchers examined how psychosocial stressors and chemical exposures interact during pregnancy, impacting birth outcomes. They focused on two primary outcomes: gestational age at delivery, and birthweight for gestational age z-scores—a standardized measure of fetal growth.

Nearly all Americans carry measurable levels of environmental chemicals, yet prior research has focused on a narrow set of well-known compounds in relation to pregnancy outcomes. Separately, psychosocial stressors have been linked to preterm birth and impaired fetal growth. Understanding how these two factors interact could help identify vulnerable populations and inform more comprehensive maternal health strategies.

The research team used data from the ECHO Cohort, a large research program supported by the National Institutes of Health, which aims to understand the effects of a broad range of early environmental influences on child health and development. The team analyzed data from 1,566 pregnant participants across 11 geographically-diverse ECHO study sites. Prenatal urine samples were tested for 113 chemicals from 10 major classes, including pesticides, plasticizers, flame retardants, and other emerging contaminants. Notably, national biomonitoring programs do not routinely measure 74 of these chemicals, making them “understudied.”

Researchers assessed psychosocial stressors using standardized measures of perceived stress, depressive symptoms, and clinically diagnosed anxiety during pregnancy and up to 8 weeks postpartum. Early-life stressors were measured using the Adverse Childhood Experiences (ACEs) scale. This scale captures stressful or traumatic experiences during childhood (up to 18 years old), including abuse, neglect, or household challenges.

To characterize chemical exposure patterns, researchers combined related chemicals into groups and used a statistical method to identify chemicals that often occur together. Birthweight and gestational age were standardized across study sites, and statistical models were stratified by stressor levels to test for changes in effect.

The study revealed that psychosocial stressors may exacerbate the impact of certain chemical exposures on pregnancy outcomes.

• Anxiety had the strongest and most consistent effect. High exposure to several phthalate classes, flame retardants, and neonicotinoids was significantly linked to shorter gestation only among mothers with prenatal anxiety. Among those without anxiety, the same exposures had little to no effect.
• Understudied chemicals also showed concerning patterns. Neonicotinoids and alternative plasticizers—often marketed as safer replacements—were associated with increased odds of preterm birth among women with clinical anxiety.
• Psychosocial stressors amplified the effects of chemical mixtures. Specific chemical mixtures (e.g., insecticides and PAHs, phthalates, and bisphenols) were linked to a higher risk of early delivery, but often only when paired with prenatal anxiety. High levels of paraben mixtures were associated with lower birthweight for gestational age only among mothers reporting high perceived stress or depressive symptoms.
• Depression and perceived stress each showed different, sometimes unexpected, patterns. In some cases, higher perceived stress was associated with longer gestation in relation to certain flame retardants, while there was no association among those with lower levels.
• Early-life adversity in mothers shaped vulnerability. Among mothers who experienced higher levels of childhood adversity (ACEs scores of 3–5), higher exposure to phthalates was linked to lower birth weight. In contrast, for mothers with no reported childhood adversity, the same chemical exposure showed almost no statistical link to birth weight.

The findings underscore the need to consider chemical exposures and psychosocial stressors together. Pregnant women with early-life adversity and anxiety may be more susceptible to the harmful effects of environmental chemicals, many of which are widespread and understudied. Additionally, stressful experiences and chemical exposures disproportionately burden socioeconomically-marginalized communities, suggesting that increased exposures may contribute to persistent disparities in birth outcomes.

This research suggests the need to examine multiple stressors simultaneously, incorporate repeated chemical measurements across pregnancy, and refine assessments of prenatal anxiety and depression. It also highlights the need for longitudinal studies to explore whether specific types of early-life stressors are particularly influential, and whether combined stress and chemical effects help explain population-level differences in birth outcomes.

Citation

Eick SM, et al. (2026). ECHO Cohort Consortium. Psychosocial stressors as modifiers of the associations between well-studied and understudied chemicals and birth outcomes in the ECHO Cohort. Environmental Pollution. Jan 15:389:127441. doi: 10.1016/j.envpol.2025.127441. Epub 2025 Nov 25. https://doi.org/10.1016/j.envpol.2025.127441. PMID: 41308729; PMCID: PMC12810359.