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 statuses with pregnancy outcomes among pregnant Iranian women, considering their baseline thyrotropin (TSH) status. We used data from the Tehran Thyroid and Pregnancy Study (TTPS), a two-phase population-based study carried out among pregnant women receiving prenatal care. By excluding participants with overt thyroid dysfunction and those receiving levothyroxine, the remaining participants (n = 1286) were categorized into four groups, according to their urine iodine status: group 1, urine iodine concentration (UIC) < 100 μg/L; group 2, UIC between 100 and 150 μg/L; group 3, UIC between 150 and 250 μg/L; and group 4, UIC ≥ 250 μg/L. Primary outcome was preterm delivery. Preterm delivery occurred in 29 (9%), 19 (7%), 15 (5%), and 8 (4%) women, 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). Adverse pregnancy outcomes are increased among women with UIC < 100 μg/L, with serum TSH concentrations ≥ 4 μIU/mL.
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The authors wish to acknowledge Ms. Niloofar Shiva for critical editing of English grammar and syntax of the manuscript. The authors would also like to thank the laboratory staff of RIES for their cooperation and assistance.
The study was approved by the ethics committee of the Research Institute of Endocrine Sciences (RIES), approval no: IR.SBMU.ENDOCRINE.REC.1397.273.
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The authors declare that they have no conflict of interest.
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Nazarpour, S., Ramezani Tehrani, F., Amiri, M. et al. Maternal Urinary Iodine Concentration and Pregnancy Outcomes: Tehran Thyroid and Pregnancy Study. Biol Trace Elem Res 194, 348–359 (2020). https://doi.org/10.1007/s12011-019-01812-5
- Iodine deficiency
- Tehran Thyroid and Pregnancy Study
- Subclinical hypothyroidism