The Vital Importance of Iodine in Pregnancy

Laura Tilt
Laura Tilt

Laura Tilt has over 10 years of experience as a dietitian, working within the NHS and private healthcare sectors and contributing to various publications, podcasts and panels. Laura is passionate about helping people understand the relationship between what’s on their plate and what goes on inside their bodies.

Iodine is an essential nutrient which we need in small amounts for the normal functioning of the thyroid gland – a small, butterfly shaped gland located at the base of the neck. 

The thyroid gland needs iodine to make thyroid hormones, which regulate most of the body’s functions including breathing and body temperature. Thyroid hormones are also essential for the growth and development of your baby and their brain during pregnancy and early life. 

What Happens If I Don’t Get Enough Iodine in Pregnancy?

A lack of iodine can lead to hypothyroidism, a condition where the thyroid gland is unable to make enough thyroid hormones. 

Hypothyroidism can bring on symptoms like constipation, fatigue, and increased sensitivity to cold. A severe iodine deficiency leads to goitre, a swelling in the neck. This happens because the thyroid gland tries to trap more iodine, causing it to become enlarged. 

Why Is Iodine Especially Important During Pregnancy? 

In the first trimester a baby’s brain grows rapidly, and thyroid hormones play an important role in regulating brain development during this period. 

The supply of thyroid hormones to a growing baby are provided almost exclusively from the mother. If material levels of thyroid hormones are low (due to a lack of iodine), levels transferred to the baby will also be lower. 

Whilst severe deficiency (which can lead to stunted mental and physical development) is uncommon in the U.K. and Western Europe, studies suggest that many pregnant women may not be getting enough iodine. This is a concern, as even mild to moderate deficiency is thought to affect the growth and intellectual development of a baby.

In one study of UK women, children born to mothers with mild to moderate iodine deficiency were more likely to have scores in the lowest quartile for verbal IQ and reading, compared to children born to mothers with sufficient iodine levels. 

As a baby’s brain continues to develop after birth, iodine is important for breastfeeding mums too, as it’s the only source of iodine for babies who are exclusively breastfed. 

How Much Iodine Do I Need During Pregnancy? 

In Europe, adults are advised to consume 150 micrograms (μg) of iodine per day, and 200 micrograms (μg) during pregnancy and breastfeeding.

It’s important to have a good iodine intake before becoming pregnant, as this helps to ensure you have good stores in your thyroid, helping levels to stay in the healthy range during pregnancy. 

What Foods Is Iodine Found In? 

Iodine enters the food chain through the soil, but due to the effects of snow, ice and rain, much of our soil and the crops grown within, are low in iodine. 

For this reason, many countries have chosen to add iodine to table salt to prevent deficiency. The U.K. doesn’t have a salt iodisation programme, but due to changes in farming practices in the 1930’s, milk and dairy foods are a good source, and are the major sources of iodine for people living in the U.K. – providing around 30-40% of our intake.

Other sources include seaweed and white fish. Seaweed isn’t recommended as a source of iodine as it can contain excessive levels, which can cause thyroid problems. You can find iodised salt in some supermarkets, but due to the link between high salt intake and blood pressure, relying on iodised salt isn’t recommended.

Iodine content (micrograms) 

  • 250ml glass cow’s milk – 75 μg
  • 150mg plain low fat Yoghurt – 51 μg
  • 30g hard cheese – 15 μg
  • 250ml fortified soya milk – ~60 μg
  • 120g Haddock – 390 μg
  • 120g Cod- 230 μg
  • 130g Plaice- 30 μg
  • 1 egg- μg 25 

Should I Take a Supplement? 

It’s difficult to get sufficient iodine unless you eat plenty of dairy foods (particularly cow’s milk) and consume iodine rich fish once or twice a week. 

If you are plant based or vegan, you will need to take a supplement. Many prenatal supplements contain between 140 micrograms and 200 micrograms of iodine, but you will need to check the label. 

It is important to note that supplements made from or containing kelp or other seaweed should not be taken during pregnancy as they can contain excessive amounts, which can be problematic.

Top Tips for Getting Enough Iodine During Pregnancy 

Eating a portion of fish twice a week and dairy products 2-3 times a day should ensure you get sufficient iodine. If you are choosing a plant milk, check to see if it is fortified with iodine, as many aren’t. 

Some types of white fish contain high levels of iodine, which can be stored in the thyroid to be used on the days of the week when you don’t eat fish. Check out our iodine rich fish recipes for ideas on dishes you can add to your diet. 

If you are concerned about your iodine intake in pregnancy, you can choose a prenatal supplement which contains iodine, and top up the remainder through diet. 

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