Pregnant women exposed to extensive environmental contamination by oxidized nitrogen compounds were studied at parturition, their neonatal health status was assessed and the involvement of oxidative stress in pathology was evaluated. Methemoglobin in maternal and cord blood was measured as a biomarker of individual exposure. Blood lipid peroxides and glutathione (reduced and total) were determined as oxidative stress biomarkers. Birthweight, Apgar scores, and clinical diagnosis at birth were used as neonatal health endpoints. Elevated exposure to oxidized nitrogen compounds was associated with increased lipid peroxidation in both maternal and cord blood. Poor birth outcome was associated with high blood lipid peroxides. Controlling for maternal age, parity, and smoking did not affect the relationships materially. The results showed that maternal/fetal exposure to oxidized nitrogen compounds is associated with increased risk of adverse birth outcome and suggest a role of oxidative damage in the pathogenic pathway.