A new study published in the journal Environmental Science & Technology has found that babies born in the early 2000s were exposed in the womb to far more per- and polyfluoroalkyl substances (PFAS) than previously detected through conventional testing methods.

Researchers from the Icahn School of Medicine at Mount Sinai analyzed archived umbilical cord blood samples collected between 2003 and 2006 and discovered evidence of widespread prenatal exposure to a broad array of so-called “forever chemicals.” The findings suggest that traditional laboratory panels significantly underestimate the range of PFAS compounds reaching developing fetuses.

PFAS are a large class of synthetic chemicals used in nonstick cookware, stain-resistant fabrics, food packaging, and firefighting foams. Known for their persistence in the environment and the human body, these chemicals have been linked in previous research to low birth weight, preterm birth, immune dysfunction, metabolic disorders, and developmental concerns.

The study drew on samples from 120 infants enrolled in the Health Outcomes and Measures of the Environment (HOME) Study, a prospective pregnancy and birth cohort based in Cincinnati, Ohio. Investigators applied both traditional targeted laboratory testing and a more expansive PFAS-focused nontargeted analysis (NTA) using high-resolution mass spectrometry.

Targeted methods measured eight well-known legacy PFAS compounds. In contrast, the nontargeted approach identified 42 confirmed or putatively identified PFAS in cord blood, including perfluorinated chemicals, polyfluorinated chemicals, and fluorotelomers. Of the 42 compounds detected through NTA, only four overlapped with those included in conventional testing panels.

The findings underscore the limitations of relying solely on predefined chemical lists when assessing prenatal exposure. By scanning broadly for hundreds to thousands of chemical features rather than restricting analysis to known compounds, the NTA method revealed a much more complex exposure landscape.

To evaluate cumulative exposure, researchers developed two scoring systems using item response theory. A “PFAS burden” score was based on concentrations from targeted testing, while a “PFAS-omics” score incorporated the relative abundance of the 42 PFAS detected through nontargeted analysis. The PFAS-omics metric was designed to provide a more comprehensive snapshot of an infant’s overall prenatal exposure at a single point in time.

Differences in findings emerged depending on which method was used. Earlier research using limited PFAS panels has reported lower PFAS levels among women who had previously given birth, suggesting that pregnancy and breastfeeding may reduce maternal body burdens of certain legacy compounds.

In the current study, targeted PFAS burden scores and concentrations of legacy compounds such as perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) were significantly lower among infants born to first-time and multiparous mothers compared with those born to mothers who had never given birth.

However, when researchers applied the broader PFAS-omics score derived from 42 compounds, no significant differences were observed across parity groups. The divergence indicates that conclusions about exposure patterns may depend heavily on how exposure is measured.

The research adds to a growing body of evidence highlighting pregnancy as a critical window of vulnerability to environmental contaminants. The American College of Obstetricians and Gynecologists has identified reducing exposure to toxic environmental chemicals, including PFAS, as a priority area for protecting maternal and child health.

Despite mounting evidence of potential health risks, PFAS exposure is not routinely measured in clinical care. The study’s authors suggest that cumulative exposure tools such as PFAS-omics scores could eventually help identify individuals or populations with higher chemical burdens and guide preventive strategies during pregnancy.

The HOME Study cohort continues to follow participants into adolescence and young adulthood, offering researchers an opportunity to examine whether higher cumulative prenatal PFAS exposure is associated with long-term health outcomes. Future work will also focus on refining PFAS-omics tools and evaluating newer or understudied PFAS compounds that may not yet be included in regulatory frameworks.

As industrial practices and chemical regulations evolve, the findings emphasize the need for more comprehensive environmental monitoring. By broadening the scope of chemical detection, researchers say public health officials and policymakers may gain a clearer understanding of the true extent of prenatal exposure to persistent synthetic chemicals — and how best to mitigate their impact.