Benefits Of Iodine In Prenatal Vitamins For Thyroid Support

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Many parents underestimate the function and importance of functional thyroid hormones throughout pregnancy. In this article, we will look into the crucial function of healthy thyroid hormones in supporting pregnancy’s well-being. Additionally, we will uncover the role of iodine in enhancing thyroid efficiency and highlight the advantages of including iodine in prenatal vitamins to support thyroid health.

The most crucial function of iodine in the body is to synthesise thyroid hormones - triiodothyronine (T3) and thyroxine (T4). These hormones are essential to regulate our overall metabolism, such as heartbeat and digestion, body temperature, and energy level. T4 is a largely inactive form of thyroid hormones (it does not impact cells; hence, it needs to be activated by converting it to T3, an active form of thyroid hormones).1

Understand thyroid health and pregnancy

During pregnancy, this butterfly-shaped gland takes on an amplified physiological function to support the healthy growth and development of the foetus. As pregnancy progresses week by week, thyroid hormones can be imbalanced, and these fluctuations are caused by increased demands on the gland to cater and adapt to the growing foetus's essentials. This mechanism is mainly caused by two pregnancy-related hormones: human chorionic gonadotropin (hCG) and oestrogen. These hormones are essential to support a growing embryo/foetus and maintain a healthy pregnancy. As a result of this amplified function, thyroid nodules experience a subtle increase in size in pregnant people. However, its enlargement is still too small to be detected by healthcare experts during routine physical examinations. 

Throughout the first few months of pregnancy, thyroid hormones are crucial for a foetus' growth, brain and nervous system development. For the first 12 weeks of pregnancy, the foetus depends entirely on maternal thyroid hormones, T4. During the same time, in weeks 10 to 12 of gestation, the foetus starts to develop and secrete TSH of its own. The foetal thyroid can also concentrate iodine and synthesise iodothyronines (enzymes that selectively remove iodide from thyroxine (T4), thus activating or inactivating these hormones).1,4

Foetal hormones, however, synthesise little of these hormones as the pregnancy enters the 18th to 20th week. Hence, foetal thyroid secretion increases gradually, which means it takes up all the iodine from the mother that could cross the placenta.1

Iodine: An elemental catalyst

At the heart of healthy thyroid function lies the importance of the mineral iodine. Iodine is crucial in the construction and synthesis of thyroid hormones. Through synthesising thyroid hormones, iodine serves as a catalyst, driving the physiological and metabolic activities, energy generation and maturation of vital organs like the brain and nervous system. 

Foods iodine can be found in include spinach, sea salts, coconut, dairy, fish and eggs. The recommended iodine intake for women is 150 μg/day (150mcg/day). It is recommended those that who are pregnant and/or breastfeeding increase their iodine intake to 250 μg/day (250 mcg/day); however, it should not exceed 500 μg/day (500 mcg/day).2,3

Several cases make our body demand more iodine and require iodine supplementations. Risk factors such as pregnancy, lactation or breastfeeding, poor diet and nutrition and eating iodine-poor soil might cause hypothyroidism and the symptoms that come with it.4 Low Iodine in the body will eventually make our thyroid gland work harder than usual. This would lead to the thyroid gland becoming swollen or one to have an enlarged thyroid called 'goitre'. 

Iodine and pregnancy: Benefits of iodine in prenatal vitamins

Typically, the essential nutritional elements for promoting a healthy pregnancy encompass macronutrients like protein, carbohydrates, dietary fibre and fats, along with micronutrients like iron, calcium, Vitamin D, Vitamin B12, zinc and iodine.5

Reading and learning about thyroid function, the effects of imbalanced hormones, and what it might do to our body during pregnancy prompted us to seek further the role of minerals, vitamins, and ions that are essential in supporting thyroid function. The most important mineral for supporting thyroid functions during pregnancy is iodine for the following reasons1,4,5

  1. Optimal Thyroid Functions - Including Iodine in prenatal vitamins is crucial in governing the production of optimal thyroid hormones essential for the foetus's growth and development. Sufficient Iodine during pregnancy also ensures the mother is not in a labile mood, tired or low in energy and provides the mother's overall sense of well-being.
  2. Elevating Maternal Wellness - Without sufficient iodine levels, mothers could experience weight loss, extreme tiredness, muscle cramps, severe constipation, preeclampsia - a dangerous rise of blood pressure in late pregnancy, and other symptoms that might endanger the baby. 
  3. Alleviate Pregnancy Complications - Iodine deficiency is proven to cause a few pregnancy complications. Having optimal iodine levels could have mitigated the risk of miscarriages, low birth weight, developmental delays, and preterm delivery. Prenatal vitamins with adequate iodine intake for a preventive mechanism reduce the chances of these complications. 
  4. Nurturing Cognitive Development - Ongoing maternal iodine deficiency (leading to Hypothyroidism) in a pregnant woman during the first trimester of pregnancy and gestational age after 18 weeks could have a detrimental effect on foetal development that might lead to permanent intellectual disability, the most severe, is known as Cretinism. Severe Iodine deficiency during pregnancy could cause babies to have problems with growth, hearing, and speech. Hence, it is important to ensure optimal iodine intake.
  5. Reduce neonatal and infant mortality - Severe iodine deficiency could increase neonatal and infant mortality. Although the mechanism of the disadvantages of iodine deficiency correlates towards infant mortality is still unknown, it is best explained that intellectually disabled babies are more prone to birth trauma, infectious disease, and nutritional deficiency, which also increases mortality. These could be prevented by optimising maternal and infant iodine intake through nutrition and supplements.

Iodine deficiency: Insights from case studies 

A study conducted in the United Kingdom on children of 8 years old born to mothers with lower urinary iodine concentrations during pregnancy noted to have lower scores for verbal intelligence, reading accuracy and comprehension when compared to children born to mothers with higher urinary iodine concentrations.6

Another case reported in Australia also noted that children born to mothers with lower urinary Iodine to creatinine concentrations had reductions in spelling, grammar and English literacy.7

A study was conducted in Spain of 150 school-age children, of whom 38% had a goitre and mild to moderate iodine deficiency reported to have increased auditory threshold/hearing loss.8

What could happen if I consume too much iodine?

Excess iodine in one's body is rare but could happen with excessive consumption of dietary supplements without a professional consultation. Having too little and too much of something is never too good. In a patient with normal thyroid function, excessive Iodine might not cause any symptoms. However, both mother and baby could be affected by excessive iodine intake. For example, the mother could have hyperthyroidism, which is problematic as too much iodine during pregnancy could lead to a phenomenon called the Wolff - Chaikoff Effect.

This is a condition where a baby suffers from hypothyroidism following the mother's excess iodine intake through pregnancy and lactation. Excess iodine from the mother's intake temporarily suppresses the baby's thyroid gland from producing thyroid hormones to protect them against hyperthyroidism. Consequently, the baby's thyroid gland does not produce sufficient thyroid hormones, thus leading to congenital Hypothyroidism.


Throughout this article, we have explored the impact of pregnancy on amplified thyroid hormones and how these hormones in pregnancy, mainly Human Chorionic Gonadotropic hormones and Oestrogens, play a role in the demand for thyroid hormones to maintain a healthy pregnancy. We highlighted iodine's pivotal role in enhancing thyroid efficiency and its advantages by including it as a prenatal vitamin to support thyroid function during pregnancy. 

Proper thyroid function is essential during pregnancy to maintain and develop a growing fetus. Hence, the increasing demand for iodine during pregnancy is expected as we go through the recommended daily iodine intake during pregnancy and lactation.

It is obvious now that mothers would require a higher level of iodine in their daily intake during pregnancy and lactation, making it a prenatal vitamin essential. As a prenatal vitamin, Iodine is vital for maintaining optimal thyroid functions and maternal wellness. It is also crucial for the development of the baby, having to avoid miscarriages, low birthweight and preterm delivery, along with reducing neonatal and infant mortality. Iodine is also vital in nourishing cognitive development.

It is recommended that pregnant women and breastfeeding mothers increase their iodine intake to 250 μg/day (0.25 mg/day) but not exceed 500 μg/day (500 mcg/day). Iodine can be extracted from products like milk, fish and eggs, which can quickly be found in your kitchen. Mothers and those lactating could also consult professional healthcare such as licensed pharmacists, nutritionists and medical doctors for blood routines to ensure their iodine and thyroid hormone levels for the possibility of taking Iodine supplements in vitamins. 

Excess iodine is rare; however, consuming too much daily without professional consultations might orchestrate another issue, such as hyperthyroidism in mothers and congenital hypothyroidism in babies. Overall, complications during pregnancy and the risk towards the baby developing problems caused by low iodine supply are undoubtedly preventable. 


  1. Yap YW, Onyekwelu E, Alam U. Thyroid disease in pregnancy. Clinical Medicine [Internet]. 2023 Mar 1 [cited 2023 Aug 10];23(2):125–8. Available from:
  2. Lee SY, Stagnaro-Green A, MacKay D, Wong AW, Pearce EN. Iodine contents in prenatal vitamins in the United States. Thyroid [Internet]. 2017 Aug 1 [cited 2023 Aug 10];27(8):1101–2. Available from:
  3. Eriksen KG, Andersson M, Hunziker S, Zimmermann MB, Moore SE. Effects of iodine-containing prenatal multiple micronutrients on maternal and infant iodine status and thyroid function: a randomized trial in the Gambia. Thyroid [Internet]. 2020 Sep 1 [cited 2023 Aug 10];30(9):1355–65. Available from:
  4. Alexander EK, Pearce EN, Brent GA, Brown RS, Chen H, Dosiou C, et al. 2017 Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and postpartum. Thyroid [Internet]. 2017 Mar [cited 2023 Aug 10];27(3):315–89. Available from:
  5. Lopes CA, Prazeres S, Martinez-de-Oliveira J, Limbert E, Lemos MC. Iodine supplementation in pregnancy in an iodine-deficient region: a cross-sectional survey. Nutrients [Internet]. 2022 Mar 27 [cited 2023 Aug 10];14(7):1393. Available from:
  6. Bath SC, Steer CD, Golding J, Emmett P, Rayman MP. Effect of inadequate iodine status in UK pregnant women on cognitive outcomes in their children: results from the Avon Longitudinal Study of Parents and Children (Alspac). The Lancet [Internet]. 2013 Jul [cited 2023 Aug 11];382(9889):331–7. Available from:
  7. Hynes KL, Otahal P, Hay I, Burgess JR. Mild iodine deficiency during pregnancy is associated with reduced educational outcomes in the offspring: 9-year follow-up of the gestational iodine cohort. The Journal of Clinical Endocrinology & Metabolism [Internet]. 2013 May 1 [cited 2023 Aug 11];98(5):1954–62. Available from:
  8. Soriguer F, Millón MC, Muñoz R, Mancha I, Siguero JPL, Aedo MJM, et al. The auditory threshold in a school-age population is related to iodine intake and thyroid function. Thyroid [Internet]. 2000 Nov [cited 2023 Aug 11];10(11):991–9.Available from:

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Nureen Izyani Binti Hashim

Doctor of Medicine, MD (Russia), MSc Public Health, Anglia Ruskin University, Essex

Dr. Izyani Hashim is a Malaysian medical doctor with several years of experience and passion for palliative and primary care and health communications. Having completed her medical degree in Russia and served as a medical doctor in Malaysia, rotating into different fields of medicine, she has gained invaluable experience in clinical care and patient interactions, enabling her to bridge the gap between complex medical information and everyday readers.

She is pursuing a Master’s in Public Health in the United Kingdom. With a mission to empower individuals with reliable health information, Dr. Izyani's articles aim to inspire healthier lives with informed choices. Her articles aim to empower populations with reliable health information, ultimately contributing to improved healthcare and well-being nationwide. presents all health information in line with our terms and conditions. It is essential to understand that the medical information available on our platform is not intended to substitute the relationship between a patient and their physician or doctor, as well as any medical guidance they offer. Always consult with a healthcare professional before making any decisions based on the information found on our website.
Klarity is a citizen-centric health data management platform that enables citizens to securely access, control and share their own health data. Klarity Health Library aims to provide clear and evidence-based health and wellness related informative articles. 
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