Maternal Urinary Iodine Concentration and Pregnancy Outcomes: Tehran Thyroid and Pregnancy Study
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Maternal Urinary Iodine Concentration and Pregnancy Outcomes: Tehran Thyroid and Pregnancy Study Zheng Feei Ma 1 Received: 12 June 2020 / Accepted: 25 August 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
In a recent study, iodine status of 1286 first-trimester Iranian pregnant women had median UIC of 142 μg/L, which indicated the presence of maternal iodine deficiency (i.e., UIC < 150 μg/L) [1, 2]. In addition, odds ratio of preterm delivery was significantly increased in Iranian women with UIC < 100 μg/L, with TSH ≥ 4 μIU/mL (OR 2.5 (95% CI 1.1, 10), P = 0.024) [1]. One limitation of the study was that UIC was not adjusted for hydration status using creatinine concentration. During pregnancy, increased glomerular filtration rate will stimulate increased urinary volume which consequently may lead to more diluted urine samples [3]. Therefore, iodine-to-creatinine (UI/Cr) ratio may better reflect maternal iodine status [4, 5]. In addition, serum thyroglobulin (Tg) should also be measured in pregnant women. When the thyroid is hyperstimulated due to iodine deficiency, increased Tg will be released from the thyroid [2]. Compared with UIC, Tg is a longer term biomarker of iodine status and might better characterize iodine status and thyroid function in pregnant women [2, 4]. Although severe maternal iodine deficiency has been associated with some adverse maternal and neonatal outcomes, it remains unclear whether mild-to-moderate maternal iodine deficiency increases the risk of developing adverse pregnancy outcomes [6]. The challenges (including the ethical concerns regarding the use of placebo in iodine deficient pregnant women, fears of possible litigation, the needs for long-term follow-up to assess maternal iodine status, lack of healthy pregnant women to volunteer, recruitment hurdles, and other operational and logis-
tics issues) for undertaking studies with iodine deficient pregnant women have limited the direct comparisons of the effect of maternal iodine deficiency on pregnancy outcomes. In addition, pregnant women might be able to physiologically cope with or adapt to low iodine intake during pregnancy for a short period of time by drawing from their intrathyroidal iodine stores [6]. Therefore, considering the impact of maternal iodine deficiency on pregnancy outcomes, relevant authorities should consider taking immediate measures (including maternal health education and promotion programs, maternal UIC screening, and fortification of staple foods with iodine) to prevent and correct iodine deficiency in pregnant women, especially in countries with low maternal iodine status and usage of iodine supplements. Although the effects of mild-to-moderate iodine deficiency may not be immediately apparent, long-term effects of iodine deficiency on vulnerable populations could more likely than not lead to adverse effects of pregnancy [6, 7].
Compliance with Ethical Standards Conflict of Interest The author declares that he/she has no conflict of interest.
References 1.
2. * Zheng Feei Ma Z
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