Prevalence of Abnormal Thyroid-Stimulating Hormone (TSH) Levels and Their Association With Iron Status in Pregnancy: A Retrospective Cross-Sectional Study

Background Thyroid hormones play a vital role in maternal metabolism and fetal neurodevelopment. Pregnancy causes physiological changes in thyroid function, particularly during the early trimesters, when rising human chorionic gonadotropin levels temporarily lower thyroid-stimulating hormone (TSH) levels before increasing later in pregnancy. Iron deficiency anemia is the most common hematologic disorder during pregnancy, mainly due to hemodilution, poor dietary intake, and short intervals between pregnancies. Because iron is required for thyroid peroxidase activity, its deficiency may lead to thyroid dysfunction. Methods A retrospective cross-sectional study was conducted from January 2023 to July 2025 across primary health care centers in Al-Ahsa, Saudi Arabia. A total of 8,542 pregnant women aged 18-40 years with singleton pregnancies and available results for hemoglobin, ferritin, and thyroid function tests were included in the analysis. Women with high-risk conditions or incomplete data were excluded from the study. Data were analyzed using IBM SPSS Statistics for Windows, Version 28 (Released 2023; IBM Corp., Armonk, New York, United States) with chi-square, Pearson's correlation, and multiple linear regression tests. A p-value less than 0.05 was considered statistically significant. The study was approved by the Institutional Review Board (IRB) of Maternity and Children Hospital, Al-Ahsa. Results A total of 8,542 pregnant women were included in the analysis, with a mean age of 29.4 years. Iron deficiency was observed in 76.6% of participants, and anemia was present in 46.2% of pregnant women. Thyroid dysfunction was identified in 2.6% of the cohort, while 97.4% were classified as euthyroid. Low ferritin and hemoglobin concentrations were each significantly associated with elevated TSH levels (p = 0.001 and p = 0.034, respectively), supporting an association between iron deficiency and thyroid dysfunction. No statistically significant associations were observed between thyroid function and either maternal age or glycated hemoglobin levels. Conclusion This study demonstrated a significant association between iron deficiency and thyroid dysfunction during pregnancy. Lower ferritin and hemoglobin levels were linked to elevated TSH, suggesting that impaired iron status may contribute to altered thyroid regulation. These findings highlight the importance of concurrent screening for iron deficiency and thyroid function in early pregnancy to improve maternal and fetal health outcomes.