• The effect of maternal urinary iodine concentration on adverse pregnancy outcomes
  • Sima Nazarpour ,1 Fahimeh Ramezani Tehrani ,2,* Mina Amiri ,3 Masoumeh Simbar ,4 Razieh Bidhendi Yarandi ,5 Fereidoun Azizi ,6
    1. Department of Midwifery, Varamin-Pishva Branch, Islamic Azad University, Tehran, Iran. / Reproductive Endocrinology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
    2. Reproductive Endocrinology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
    3. Reproductive Endocrinology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
    4. Midwifery and Reproductive Health Research Center, Department of Midwifery and Reproductive Health, School of Nursing and Midwifery, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
    5. Reproductive Endocrinology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
    6. Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran


  • Introduction: Iodine is essential for the production of thyroid hormones, and its deficiency during pregnancy may be associated with poor obstetric outcomes. The aim of this study was to investigate the relationship between maternal iodine status with pregnancy outcomes among pregnant Iranian women, considering their baseline thyrotropin (TSH) status.
  • Methods: We used data from Tehran Thyroid and Pregnancy Study (TTPS); a two-phase population-based study carried out among pregnant women receiving prenatal care in centers, under the coverage of Shahid Beheshti University of Medical Sciences. By excluding participants with overt thyroid dysfunction and those received levothyroxine, the remaining (n = 1286) were categorized in four groups, according to their urine iodine status: group 1: urine iodine concentration (UIC) < 100 μg/L, group 2: UIC = 100–150 μg/L, group 3: UIC = 150 - 250 μg/L and group 4: UIC ≥ 250 μg/L. The Primary outcome was preterm delivery.
  • Results: In a total of 1286 pregnant women, median (interquartile range) of UIC was 142.3 (133.6) μg/L and 370 (28.8%), 315 (24.5%), 359 (27.9%) and 242 (18.8%) of pregnant women had UIC levels < 100 μg/L, 100- 150 μg/L, 150-250 μg/L and ≥ 250 μg/L, respectively. Preterm delivery occurred in 29 (9%), 19 (7%), 15 (5%) and 8 (4%) and neonatal admission was documented in 22 (7%), 30 (12%), 28 (11%) and 6 (3%) women of groups 1, 2, 3 and 4 respectively. Generalized Linear Regression model (GLM) demonstrated that the odds ratio of preterm delivery was significantly higher in women with urinary iodine < 100 μg/L and TSH ≥ 4 µIU/ml than those with similar urinary iodine with TSH < 4 µIU/ml [OR: 2.5 (95% CI: 1.1, 10), p = 0.024].
  • Conclusion: Adverse pregnancy outcomes are increased among those ones with UIC < 100 μg/L, with serum TSH concentrations ≥ 4 μIU/mL. Despite the implementation of iodized salt strategies in Iran, mild iodine deficiency among our pregnant cohort, indicate that iodine supplementation needs to be implemented for pregnant women. Considering the adverse pregnancy outcomes due to iodine deficiency, especially in women with TSH ≥ 4 μIU/mL, monitoring of urinary iodine concentration at the population level and iodine replacement may be needed during pregnancy, even in areas of iodine sufficiency.
  • Keywords: Iodine deficiency, pregnancy, outcomes, Tehran Thyroid and Pregnancy, subclinical hypothyroidism.