Iodine deficiency is widespread across Australia and New Zealand due to low soil iodine levels and a diet generally lacking in iodine-rich foods. In contrast, populations that consume seaweed and fish daily tend to have significantly better iodine status.
Why Iodine Matters in Pregnancy
It’s well established that iodine supplementation is one of the essential building blocks during pregnancy, especially for optimising your baby’s brain development and cognitive function.1-3
A maternal iodine deficiency can lead to a range of serious outcomes, including goitre, cretinism, and congenital anomalies, as well as miscarriage, stillbirth, or an infant with reduced IQ, learning difficulties, motor skill issues, or hearing impairments.4
One biological challenge is that pregnancy increases renal clearance of iodine, meaning more iodine is lost through urine. Maintaining normal thyroid function during pregnancy therefore requires consistent dietary iodine intake.5
Dietary Sources of Iodine
Good dietary sources of iodine include eggs, fish, seafood, and seaweed (such as in miso soup). Using iodised or Himalayan crystal salt can also help, ¼ teaspoon of Himalayan salt contains around 100 mcg of iodine, compared to 71 mcg in the same amount of iodised salt.
How Much Iodine Do You Need in Pregnancy?
The recommended dietary intake (RDI) of iodine during pregnancy is 220 mcg per day. However, more is not necessarily better. During the first trimester, the pregnancy hormone human chorionic gonadotropin (hCG) naturally stimulates the thyroid, and excessive iodine supplementation can over-stimulate thyroid function, potentially worsening morning sickness symptoms.6,7
How to Test Iodine Levels
The most accurate way to assess iodine status is through thyroid function testing (blood tests). A urinary iodine test can indicate recent iodine intake from diet, but it is not a reliable measure of total body iodine levels.
Ensuring optimal iodine levels before and during pregnancy supports both maternal thyroid health and your baby’s brain development. If you’re unsure about your iodine intake or thyroid function, speak with your healthcare practitioner for personalised guidance.
Final thoughts
Ensuring you get the right amount of iodine during pregnancy is a simple yet powerful way to support both your health and your baby’s development. While it’s important not to over-supplement, maintaining adequate intake through diet and a well-balanced prenatal vitamin can make a significant difference to thyroid function and cognitive outcomes for your child. If you’re unsure about your iodine status or supplement needs, speak with your healthcare practitioner for individual advice, supporting your thyroid now helps lay the foundation for your baby’s lifelong wellbeing.
References
- Monahan, M., et al. Costs and benefits of iodine supplementation for pregnant women in a mildly to moderately iodine-deficient population: a modelling analysis. The Lancet Diabetes & Endocrinology, 2015; 3(9): 715–722.
- Sukkhojaiwaratkul, D., et al. Effects of maternal iodine supplementation during pregnancy and lactation on iodine status and neonatal thyroid-stimulating hormone. J Perinatol, 2014; 34(8): 594–598.
- Morse, N.L. Benefits of docosahexaenoic acid, folic acid, vitamin D and iodine on foetal and infant brain development and function following maternal supplementation during pregnancy and lactation. Nutrients, 2012; 4(7): 799–840.
- Hamaoui, E. and M. Hamaoui. Nutritional assessment and support during pregnancy. Gastroenterol Clin North Am, 2003; 32(1): 59–121.
- Forbes, S. Pregnancy sickness and parent-offspring conflict over thyroid function. J Theor Biol, 2014; 355: 61–67.
- Ballabio, M., Poshyachinda, M. & Ekins, R.P. Pregnancy-induced changes in thyroid function: role of human chorionic gonadotrophin as putative regulator of maternal thyroid. J Clin Endocrinol Metab, 1991; 73(4): 824–831.
- Luetic, A.T.M., B. Is hyperthyroidism underestimated in pregnancy and misdiagnosed as hyperemesis gravidarum? Med Hypotheses, 2010; 75(4): 383–386.
