Sociodemographic and Reproductive Correlates of Per- and Polyfluoroalkyl Substance Concentrations in a Preconception Cohort Study

Background: Per- and polyfluoroalkyl substances (PFAS) are endocrine-disrupting chemicals associated with adverse reproductive health outcomes (e.g., reduced fecundability). Identifying correlates of PFAS exposure in females is therefore an important public health objective, but less research has been conducted in the preconception period. Methods: We evaluated correlates of PFAS exposure using cross-sectional data from 449 participants enrolled in Pregnancy Study Online, a preconception cohort study, during 2014–2023. We measured concentrations of four PFAS in serum ( n = 293) or capillary whole blood ( n = 156) at baseline (preconception). Participants reported sociodemographic and reproductive history correlates at baseline. We used multivariable linear regression models to assess associations between correlates and PFAS concentrations, adjusting for all correlates, sampling year, and biospecimen sample type. We estimated percent differences in PFAS concentrations with 95% confidence intervals (CIs). Results: Demographic correlates (higher education, non-Hispanic White race and ethnicity, being married) were associated with higher PFAS concentrations. We observed geographical differences in PFAS concentrations, but limited association with tap water consumption. Typical menstrual characteristics, especially flow intensity and cycle length, were associated with lower PFAS concentrations, notably, perfluorooctanesulfonic acid (moderate versus light flow: β = −31.4%, 95% CI = −53.6%, 1.5%; 27–29 days versus <27 days of cycle length: β = −28.4%, 95% CI = −43.3%, −9.5%). Longer breastfeeding duration and later sampling year were consistently associated with lower PFAS concentrations. Conclusion: Several demographic and reproductive correlates were associated with PFAS concentrations among pregnancy planners. These findings can help to identify females at increased risk for PFAS exposure in the sensitive preconception period.