The Dangers Of Iodine Deficiency In Pregnancy: How To Prevent It Through Food

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Did you know that 10g of dried nori seaweed has 232 mcg of iodine? That’s enough for pregnant women like you to meet the 250 mcg daily requirement! (1)

Aside from seaweed, many other food sources can also help to elevate your iodine levels while decreasing your risk of iodine deficiency, which can cause possible health complications for you and your baby.

Iodine deficiency in pregnancy is a critical issue that moms shouldn’t ignore.

It can lead to miscarriage, stillbirth, low birth weight, and serious congenital complications such as cretinism or cognitive disability. (2)

What Is Iodine & What Happens When A Pregnant Woman Has Iodine Deficiency Disease?

Iodine is a trace element that our bodies need for thyroid hormone synthesis, the process of creating thyroid hormones such as T3 and T4.

The human body doesn’t produce this micronutrient on its own, but you can get plenty of iodine from many different food sources.

Iodine is a vital nutrient during pregnancy.

In fact, your iodine needs increase by at least 50% while pregnant because a good portion of your intake goes directly to your baby.

During gestation, you’re producing thyroid hormones for both of you, and according to the ATA (American Thyroid Association), your baby needs this mineral for proper fetal development. (3)

How Do Thyroid Hormones Impact Fetal Brain Development?

Did you know that even moderate iodine deficiency can put your child at risk of potentially experiencing brain development problems?

Your baby’s central nervous system attunes with your thyroid status.

That’s why it’s important that your body has adequate thyroid hormone production during pregnancy.

These thyroid hormones are transported to your baby through the placenta to help in their brain development.

Iodine deficiency-related problems with your baby’s brain development might lead to severe cognitive disability, as explained in a 2005 study in PubMed. (4)

The best example is the prevalence of severe intellectual disability in areas like Papua New Guinea, where iodine insufficiency still remains a problem. (4)

When Is Iodine Most Important During Pregnancy?

It’s important to note that neurodevelopmental problems observed in the first trimester of pregnancy are irreversible after birth. (5)

That’s why it’s important to have adequate iodine levels, especially during early pregnancy.

Do Low Iodine Levels Make It Harder To Conceive Or Increase The Risk Of Miscarriage?

Some research does seem to suggest that iodine deficiency could negatively impact fertility.

A 2018 study on 467 women trying to get pregnant showed that those with an iodine-creatinine ratio lower than 50 mcg/g had a 46% lesser chance of getting pregnant than those with levels over 100 mcg/g. (6)

Meanwhile, a 2012 literature review in the Indian Journal of Endocrinology and Metabolism showed that women with subclinical hypothyroidism have an increased risk of the following: (7)

  • Miscarriage
  • Perinatal mortality (stillbirth)
  • Pre-eclampsia (a serious pregnancy complication involving high blood pressure and possible organ damage to the liver and kidneys)

So, it’s really best to keep your iodine levels within the normal range and check your thyroid function before conception if you’re planning to get pregnant soon.

What Is The First Symptom Of Iodine Deficiency?

The symptoms can vary among patients. But you can watch out for the following iodine deficiency signs: (8)

  • Hair loss
  • Tiredness
  • Shortness of breath
  • Dry skin

Other symptoms can include: (9)

  • Cold intolerance
  • Voice hoarseness
  • Sleepiness
  • Impaired memory
  • Paresthesia (abnormal tingling or prickling sensation on your hands)
  • Constipation
  • Weight gain
  • Slowed movements
  • Mental impairment
  • Slower heart rate

How Can I Get The Right Amount of Iodine Through My Food & Supplements?

Most people can get optimal iodine nutrition from food. If that’s not enough, iodine supplements can also help you reach optimal levels during pregnancy.

Based on the recommendations from the ICCIDD (International Council for the Control of Iodine Deficiency Disorders), UNICEF (United Nations Children’s Fund), and WHO (World Health Organization), daily iodine requirements for adults are 150 mcg and 250 mcg per day for pregnant women. (1)

Which Foods Are Rich In Iodine?

These are foods rich in dietary iodine:

  • Dairy products such as kefir, cheese, milk, and yogurt
  • Beef liver
  • Eggs
  • Some low-mercury fish and seafood such as cod and shrimp
  • Seaweed such as dulse, kelp, and nori
  • Bread made with iodate dough conditioner
  • Iodized salt

Due to global salt iodization programs, 76% of households worldwide are adequately consuming iodized salt. (10)

But take note, moms: Not all salts you can buy from the grocery store are iodized.

For example, Kosher salt and sea salts have become a popular choice in the US. But a 2013 study pointed out that these actually have no iodine content, so be sure to check your salt labels. (11)

Another potential drawback of only using iodized salt for your required daily intake is that iodized salt can actually lose its iodine content within 6 months.

This means that if you don’t consume your iodized salt quickly, you might be getting less than you bargained for.

A 2002 study found that salts lose their iodine content in areas with at least 50% relative humidity. That’s a big reason why you can’t just rely on iodized salt for your dietary needs. (12)

For proper maternal thyroid function, moms should really try to get adequate iodine from the above-listed food sources.


Thankfully, daily supplementation with 150 mcg of potassium iodide solved the iodine deficiency problem in regions with difficult access to iodine-rich foods. (11)

If you think you’re having trouble getting the right amount of iodine from food, talk to your doctor about the right supplementation options for you.

Iodine supplementation in iodine-deficient mothers can help to improve the child’s emotional and learning outcomes.

However, clinical trials suggest that a supplementation delay of 6-10 weeks could increase the risk of neurodevelopmental problems in the baby.

Children of moms with delayed supplementation and those who didn’t receive any supplementation had lower neurobehavioral performance.

Children whose moms had proper iodine intake starting from early pregnancy did not show any delay in child development. (13)

That’s why you need to have proper iodine nutrition starting at 4-6 gestational weeks up to the end of lactation.

Should I Check My Iodine Levels During Pregnancy?

Currently, there are no recommendations for routine iodine testing in pregnant women. That’s mainly due to difficulties in finding a test that can accurately measure iodine levels in the body. (14)

According to the WHO’s “Assessment of Iodine Deficiency Disorders and Monitoring Their Elimination” manual, a person’s iodine status determines the amount of iodine in their thyroid gland and whether there’s enough iodine for the gland to function normally. (15)

While you might not be able to check your exact iodine levels in pregnancy, you can most certainly check your thyroid hormone levels, and this can indicate whether you’re adequately supplementing or not.

Pointing out the high risk of bias as shown in observational studies, researchers listed the following as valuable biomarkers of iodine status: (16)

  • TSH (Thyroid-stimulating hormone)
  • Serum T4 (thyroxine)
  • Serum T3 (triiodothyronine)
  • Tg (Thyroglobulin)
  • UIC (Urinary iodine concentration)

TSH Hormone Levels & Thyroid Function In Pregnancy

TSH levels in your blood show whether your thyroid gland (a small, hormone-producing organ located at the front of your neck) works properly.

High TSH levels indicate that you might have an underactive thyroid, while low TSH results indicate you might have an overactive thyroid.

Iodine status in pregnant women may also be determined using thyroid volume by ultrasound. (17)

When iodine levels are sufficient, thyroid volume increases in pregnant women during the third trimester compared to the first trimesterand then decreases after birth. (18)

Researchers believe this is due to changing TSH and BMI (body mass index) levels throughout pregnancy.

What Are The Different Levels Of Iodine Deficiency?

The following median urinary iodine concentrations (MUIC) indicate adequate iodine intake:

  • 150 to 249 mcg/L for pregnant women
  • >100 mcg/L for breastfeeding women

MUIC below these levels indicates iodine deficiency. (19)

Levels of iodine micronutrient deficiency:

  • Mild iodine deficiency, 120 to 149 mcg/L
  • Moderate iodine deficiency, 26 to 119 mcg/L
  • Severe iodine deficiency, <25 mcg/L

Note that all levels of iodine deficiency affect maternal and neonatal thyroid function. (20)

Severe iodine deficiency needs immediate correction because this may link to more prominent abnormalities. (21)

The Dangers of Iodine Deficiency In Pregnancy

Did you know that around 38 million babies are affected by iodine deficiency in developing countries? This still happens despite salt iodization programs. (22)

Moreover, a 2020 cross-sectional study published in the European Journal of Nutrition discovered that iodine status remains low in a population of vulnerable groups, even in areas with salt iodization such as Switzerland. (23)

Numerous clinical trials have established the effects of iodine deficiency in pregnancy and gestation. (24)

The long-term consequences of iodine deficiency are a serious matter.

Even mild maternal iodine deficiency can cause cognitive impairment in children. (2)

Areas with dietary iodine deficiency show a prevalence of combined maternal and fetal hypothyroidism that could lead to:

  • Neurological cretinism manifested as:
    • Impaired gait and motor function
    • Lower IQ (intelligence quotient)
  • Goiter (abnormal enlargement of the thyroid gland) of mother and baby

Iodine-deficient areas have more cases of impaired motor and visual perception, reveals a 2001 meta-analysis in The Journal of Clinical Endocrinology & Metabolism. (25)

Moreover, children exposed to severe iodine deficiency displayed a lower IQ score. (26)

Maternal iodine status is also associated with their children’s language skills from infancy to toddlerhood.

A study comprising 39,471 Norwegian mothers and children found a link between neurodevelopment and iodine deficiency. (27)

Moms with low iodine intake during pregnancy (UIC below 100 mcg/L) have an increased risk of having children with language delays and more unsatisfactory school performance.

Iodine deficiency may also lead to reduced physical growth in children. (28)

But iodine treatment can improve your baby’s cognitive development if provided during the first and second trimesters. (29)

What Are The Effects Of Excess Iodine In Pregnancy?

If you’re worried about low iodine levels, you should also watch out for excess iodine in pregnancy. It’s due to these factors: (30)

  • Too much iodine supplementation
  • Improper diet
  • Effects of medications
  • Medical tests using iodinated contrast agents
  • Use of topical iodine
  • Iodine exposure from environmental contaminants (radiation fallout)

Excess iodine levels are defined as >300 mcg/l for children and >500 mcg/l for pregnant and lactating women. (15)

A 2005 study of 6,010 pregnant women in China showed that women with high iodine levels have a risk of thyroid dysfunction. (31)

Other adverse effects of excess iodine levels: (32)

  • Iodine-induced hyperthyroidism (overactive thyroid)
  • Iodine-induced hypothyroidism (underactive thyroid)
  • Autoimmune thyroid inflammation
  • Postpartum thyroid inflammation

The prevalence of hyperthyroidism is relatively low at only around 2/1000 pregnancies, but this condition is associated with: (33)

  • Excess of thyroid hormones in the baby’s body
  • GD (Graves’ disease), an autoimmune condition
  • Persistent nausea and vomiting during pregnancy

Therapy for hyperthyroidism is needed because it can lead to:

  • Low birth weight
  • Premature labor
  • Heart failure
  • Pre-eclampsia
  • Risk of fetal loss

In a 2006 controlled trial in The Journal of Clinical Endocrinology & Metabolism, researchers concluded that Levothyroxine therapy lowered the chances of premature delivery and miscarriage in women with autoimmune thyroid disease. (34)

Because both iodine deficiency and excess levels cause health issues in pregnant women, you should take just what’s enough for you and your baby.

Make sure it’s just within the 220-250 mcg daily requirement.

How Common Is Iodine Deficiency In Pregnancy?

Your baby gets most of their nutrients from you. That’s why many pregnant moms commonly experience moderate deficiencies of certain nutrients and essential minerals.

Some studies suggest that as many as 85% of pregnant women may have a moderate iodine deficiency. (35)








(7) Sarkar D. (2012). Indian J Endocrinol Metab, Suppl 2.

(8) Carlé A, Pedersen IB, Knudsen N, Perrild H, Ovesen L, Laurberg P. 2014. Eur J. Endocrinol.









(17) WHO/UNICEF/ICCIDD consultation. Geneva, Switzerland. (1992)



(20) Delange F.

(21) Laurberg P, Bülow Pedersen I, Knudsen N, Ovesen L, Andersen S.

(22) Alex Stagnaro-Green and Elizabeth N Pearce. 2013. The Lancet. DOI:

(23) Andersson M, Hunziker S, Fingerhut R, Zimmermann MB, Herter-Aeberli I. in Eur J Nutr.

(24) ALSPAC (Avon Longitudinal Study of Parents and Children).


(26) Qian M, Wang D, Watkins WE, Gebski V, Yan YQ, Li M, Chen ZP. 2005. Asia Pac J Clin Nutr.



(29) Cao XY, Jiang XM, Dou ZH, et al. 1994. Google Scholar




(33) Glinoer G. 1997. The Journal of Endocrine Reviews.

(34) Negro R, Formoso G, Mangieri T, Pezzarossa A, Dazzi D, Hassan H. 2006. J Clin Endocrinol Metab.


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