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Iodine is a chemical element and what’s called a trace nutrient, a chemical that your body needs, but in very small concentrations, and that is present in food and in the environment. Like all elements, iodine can exist in elemental form (meaning molecules containing only iodine) or it can exist as part of chemical compounds (molecules that contain iodine along with other elements). In your diet, iodine usually exists as iodide; this is to say an ion (a charged particle) that is part of a salt (as in sodium iodide or potassium iodide). Iodide salts are what are added to table salt.
Your body needs iodine in order to manufacture the thyroid hormones thyroxine (called T4) and triiodothyronine (called T3). In order for your thyroid gland to make enough T3 and T4 during pregnancy, the requirement for iodine increases. If you are breastfeeding then the requirement increases further after you deliver your baby. If you do not take in enough dietary iodine, you will not make enough T3 and T4 and your thyroid will grown. It will create a lump in your neck that can trigger a cough and make it difficult to swallowing. Doctors call this condition goiter and it can happen before the development of any other symptoms resulting from a reduction in thyroid hormone levels, such as feeling cold and fatigue.
As for how much iodine is the right amount, during pregnancy, you should consume at 220 micrograms (mcg) or more per day of iodide. You will be at risk of not getting enough iodine if you consume food grown in regions with low iodine levels in the soil. Such regions include mountainous areas of Asia and South America. Of course, you also are at risk if you avoid iodized salt. Another practice that puts you at risk of low iodine is if you consume large quantities of foods that interfere with the movement of iodine into the thyroid. Such foods include soy, cassava, cabbage, broccoli, and cauliflower. Iodine deficiency is rare in North American and western Europe, but pregnant women may occasionally mild to moderate iodine deficiency on occasion, enough to produce goiter, because of the increased need for iodine that develops during pregnancy. Along with your thyroid, iodine is also important to the development of the fetus that is growing inside your womb. This is the reason for the increased iodine need during pregnancy.
On the other hand, if your intake of iodine is excessive, this can cause your thyroid to become overactive. To avoid this complication, it is important that you avoid consuming more than 1,100 mcg per of iodide per day. In other words, the safe range for iodide intake during pregnancy is 220-1,100 mcg per day.
As noted earlier, too much iodine or iodide in your diet can give you an overactive thyroid; the medical term for this is hyperthyroidism. If this happens, it can make it more difficult for you to get pregnant in the first place. You also can have difficulty getting pregnant if your male partner is hyperthyroid, because he is consuming too much iodine. Excessive iodine intake is very rare, though. Iodine deficiency, which causing an underactive thyroid, known as hypothyroidism, is another situation that can reduce your fertility. Furthermore, excessive iodide and iodide deficiency can cause spontaneous abortion (miscarriage) once you are pregnant. Thus, you can optimize your capability of becoming pregnant and staying pregnant by seeing that you get adequate but not excessive levels of iodine in your diet.
Radioactive iodine is a form of iodine that is used to treat certain thyroid conditions. Exposure to radioactive iodine has been linked to birth defects, but birth effects happen much more often due to iodine deficiency. Maternal iodine deficiency can lead to severe developmental abnormalities of the brain, often causing mental retardation, hearing problems, and other abnormalities.
The take-home lesson here is that iodine is a nutrient, so you need to receive adequate, but not excessive amounts, in your diet. This is vital both to the fetus while you are pregnant, and to the newborn baby while you are nursing.