Predicted values (95% confidence intervals) of specific gravity-corrected urinary oxidative stress biomarker concentrations by gestational age at sample collection from generalized additive models adjusted for random intercepts only. Biomarker concentrations at visits 1 (V1; median 10 weeks gestation), 2 (V2; median 15 weeks gestation), 3 (V3; median 26 weeks gestation), and 4 (V4; median 35 weeks gestation) plotted for reference. *Denotes significant difference (p<0.05) in urinary biomarker concentration for the respective visit compared to visit 1, tested using linear mixed model with random intercepts only. Abbreviations: 8-OHdG, 8-hydroxydeoxyguanosine.