Maternal vitamin D, oxidative stress, and pre‐eclampsia

Objective To examine the associations between risk of pre‐eclampsia and pregnancy levels of maternal 25‐hydroxyvitamin D (25[OH]D) and oxidative stress biomarkers. Methods A nested case–control study (n = 99; 34 cases; 65 controls) within a prospective pregnancy cohort. Maternal 25(OH)D and oxidative stress markers (six isomers of F2‐isoprostanes; F2‐isoPs) were measured in plasma at 12–18 and 24–26 gestational weeks. Vitamin D deficiency was defined as 25[OH]D less than 50 nmol/L. Results Maternal vitamin D deficiency was associated with increased 8‐iso‐PGF2α (P = 0.037), 15(R)‐PGF2α (P = 0.004), (±)5‐iPF2α‐VI (P = 0.026) at 12–18 weeks. Vitamin D deficiency was inversely associated with 8‐iso‐PGF2α (P = 0.019) and (±)5‐iPF2α‐VI isomer (P = 0.010) at 24–26 weeks. Both maternal vitamin D deficiency (adjusted odds ratio [aOR], 4.79; 95% confidence interval [CI], 1.67–13.75) and increased (±)5‐iPF2α‐VI (aOR, 2.46; 95% CI, 1.16–5.22) at 24–26 weeks were associated with risk of pre‐eclampsia. However, the interaction test between 25(OH)D and (±)5‐iPF2α‐VI was not significant (P = 0.143). Conclusion Plasma 25(OH)D below 50 nmol/L was associated with increased oxidative stress levels during pregnancy as measured by two F2‐isoP isomers, including the well‐studied marker 8‐iso‐PGF2α. Whether vitamin D‐induced oxidative stress mediates the risk of pre‐eclampsia warrants future study. Synopsis In pregnancy, plasma 25‐hydroxyvitamin D levels lower than 50 nmol/L were associated with both increased oxidative stress measured as F2‐isoprostanes and increased risk of pre‐eclampsia.