Pregnancy Sickness Linked To Iodine Levels, Study Says

Pregnancy Sickness Linked To Iodine Levels, Study Says

Whether it’s that slightly queasy feeling or the full-blown vomiting every day, most pregnant women will experience some form of pregnancy sickness.

In fact, up to 75% of pregnant women have some nausea or vomiting during the first trimester.

Most women would do anything to avoid feeling constantly seasick for weeks on end, or to put an end to the early morning gagging that accompanies the first trimester.

Pregnancy Sickness Linked To Iodine Levels, Study Says

Morning sickness has always been attributed to increasing hormonal changes in the first trimester.

New research has now come to light. It suggests pregnancy nausea might be caused by the embryo’s need for iodine.

What Causes Pregnancy Sickness?

Experts aren’t exactly sure what causes pregnancy sickness, but the most popular belief is it’s caused by the body’s reaction to the pregnancy hormone, human chorionic gonadotropin (hCG).

During the first trimester, this hormone is produced at higher levels than at any other time during pregnancy, which led to the belief it was the hormonal culprit responsible for pregnancy sickness.

However the correlation between hCG levels and pregnancy sickness hasn’t been well established.

During early pregnancy, hCG also acts as a thyroid stimulator. Higher levels of hCG prompt increased production of a thyroid hormone called thyroxine.

This has led experts to believe hCG ensures the production of essential thyroid hormones during pregnancy.

However, other experts believe the embryo uses hCG to ‘hijack’ the maternal thyroid system and release stored iodine.

What Did This Research Show?

Biology professor Scott Forbes’ research paper, published in the Journal of Evolution and Human Behavior, suggests pregnancy sickness is a way for the embryo to get access to necessary iodine.

For a long time, experts believed pregnancy nausea to be a protective mechanism, to protect the growing embryo from hazards such as toxins or bacteria.

Professor Forbes says his research debunks this belief. In his review of the importance of iodine during pregnancy, Forbes describes what he calls an ‘antagonistic pleiotropy’ between mother and embryo – essentially a tug of war over who gets the necessary iodine.

In other words, the embryo is using hCG to hijack the mother’s thyroid function, so as to get the iodine it needs.

When iodine is readily available, the embryo’s continuing demands for iodine create inert metabolites of thyroid hormones. This leads to mild, moderate or severe pregnancy sickness symptoms in the mother.

What Does Iodine Have To Do With It?

Iodine is trace mineral, and an essential building block of the thyroid hormones triiodothyronine (T3) and thyroxine (T4).

In the body, these hormones regulate the metabolic activities of almost all our cells, heart and digestive functions, muscle control, brain development, and maintenance of bones.

They also play a critical role in early fetal development of most organs, especially the brain.

During pregnancy, iodine requirements increase, but too much or too little iodine during early pregnancy can damage the developing embryonic brain.

You can read more here in Iodine Deficiency And Pregnancy – What You MUST Know.

How Do I Find Out About My Iodine Levels?

According to the World Health Organization, iodine deficiency affects over 70% of the world’s population.

Unlike other nutrients, such as iron or calcium, iodine doesn’t occur naturally in foods produced on land. It is present in soil, however, and we consume it when we eat foods grown on that soil.

Iodine levels in soil can vary, depending on region. Mountainous areas are naturally low in iodine; other areas might have become depleted due to industrial or agricultural practices, and environmental pollutants.

Foods that come from the sea – such as fish, seaweed and sea vegetables – are richer in iodine.

Many countries have introduced iodine fortification of breads and salt, in an attempt to make up the deficiency of iodine intake. This hasn’t stemmed the tide of iodine deficiency.

If you are planning on becoming pregnant, it would be wise to have your iodine levels tested. You can talk to your care provider about having a simple urine test done.

Try to achieve and maintain good iodine levels during your pregnancy. It’s critical for your baby’s development.

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Sam McCulloch enjoyed talking so much about birth she decided to become a birth educator and doula, supporting parents in making informed choices about their birth experience. In her spare time she writes novels. She is mother to three beautiful little humans.


  1. I went through the same thing. I put ice cubes in my mouth and I wanted to puke… I put water in my mouth, I wanted to puke again…
    Crackers didn’t work for me either. No to morning sickness tea, however, helped to soothe me from that horrible nausea!!

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