Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 0 0 2026 09 12 1 21 Na Liu Department of Obstetrics, Beijing Friendship Hospital, Capital Medical University, Beijing, China Yan long Department of Obstetrics, Beijing Friendship Hospital, Capital Medical University, Beijing, China 2026 05 14 2026 06 14 Hypertensive disorders of pregnancy (HDP), particularly preeclampsia, involve immune-endocrine dysregulation, oxidative stress, and endothelial dysfunction. This systematic review and meta-analysis evaluated associations between urinary iodine concentration (UIC), HDP, and related biomarkers. PubMed was searched from inception to February 2026, with additional manual screening. Thirteen studies were included, and six underwent meta-analysis. Women with HDP/preeclampsia had lower UIC than controls (MD −143.647 μg/L; 95% CI −256.362 to −30.933; I²=97.8%). TSH and FT3 did not differ significantly, whereas FT4 was reduced in HDP (MD −1.007 pmol/L; 95% CI −1.660 to −0.354; I²=0%). Qualitative evidence indicated alterations in TPOAb, TgAb, CRP, nitric oxide, TBARS, SOD, CAT, OxLDL/Alb, GGT, and lymphocyte percentage. Abnormal iodine status may contribute to HDP through thyroid dysfunction, immune imbalance, oxidative stress, and endothelial inflammation. Reduced FT4 was the most consistent biochemical abnormality. Further standardized, large-scale studies are needed. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/4836 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/4836/2420