SummaryBackgroundPrenatal exposures to persistent organic pollutants (POPs) have been associated with asthma medication use and self‐reported symptoms, but associations with lung function and allergic sensitization have been minimally explored. The aim of the study was to examine the associations between prenatal exposures to POPs and allergic sensitization and lung function in 20‐year‐old offspring.MethodsIn a Danish cohort of 965 pregnant women established in 1988–1989, six polychlorinated biphenyl (PCB) congeners, hexachlorobenzene (HCB), and dichlorodiphenyldichloroethylene (p,p’‐DDE) were quantified in archived maternal serum drawn in gestational week 30 (n = 872). Among those with available maternal exposure information, at age 20, 421 offspring attended attended a clinical examination including measurements of allergic sensitization (serum‐specific IgE ≥ 0.35 kUA/L) (n = 418) and lung function [forced expiratory volume in one second (FEV1) and forced vital capacity (FVC)] (n = 414).ResultsThere were no associations between maternal concentrations of POPs and offspring allergic sensitization at 20 years of age. Maternal concentrations of POPs were, however, positively associated with offspring airway obstruction (FEV1/FVC < 75%). Compared to offspring in the first tertile of exposure, offspring in the third tertile of dioxin‐like PCB exposure had an OR of 2.96 (95% CI: 1.14–7.70). Similar associations for non‐dioxin‐like PCBs, HCB, and p,p’‐DDE were 2.68 (1.06–6.81), 2.63 (1.07, 6.46), and 2.87 (1.09, 7.57), respectively. No associations were observed with reduced lung function (FEV1% of predicted value < 90%).Conclusion and Clinical RelevanceOur data indicate that prenatal exposure to POPs appears to be associated with airway obstruction but not allergic sensitization at 20 years of age. The findings support that chronic obstructive lung diseases may have at least part of their origins in early life.