The World of Pregnancy

Iodine While Pregnant: What Is Its Role & Why Do Its Requirements Increase?

Did you know that one of the important minerals required during a pregnancy is iodine? In today`s article we`ll try to outline more important information about its role in the organism, sources where to find it or why do women who are pregnant or breastfeeding need more iodine.

Iodine During Pregnancy

What Is Iodine & What Is Its Role?

Iodine is a microelement, which means that it can be found in small amounts in the human organism (15 – 20 mg for adults). Its role is the one of a substrate for the synthesis of the thyroid hormones. These hormones play an essential role in the brain development and nervous system before birth. Thyroid hormones are very important in the development of other organs as well as in the growth process of the baby. Children with hypothyroidism untreated during childhood may present a growth deficit, also known as nanism, and delayed puberty.

Iodine deficiency is the most common cause of mental retardation which can be prevented. Lack of iodine may result in a decreased maternal as well as fetal thyroid capacity to produce sufficient amounts of thyroid hormones, a condition known as hypothyroidism, in severe forms leading to mental retardation. It was demonstrated that mild iodine deficiency forms have side effects, such as a decreased IQ potential with up to 13.5 points.

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Iodine cannot be synthesized by the human organism, therefore an adequate intake of iodine is essential for any pregnant woman or a woman who is breastfeeding.

What Is the Recommended Amount of Iodine?

If for an adult, the necessary intake of iodine is of 250 µg/day, for a pregnant or breastfeeding woman it`s only logical for the iodine necessary intake to be higher. According to WHO, the latest studies recommend an increase of iodine from 200 to 250 µg/day. The American standards recommend 150 µg/day for a woman who wants to become pregnant, 220 µg/day for a pregnant woman and 290 µg/day for a woman who is breastfeeding.

Age, Population Group Iodine Intake (μg / day)
Newborn 0 – 6 years 110
Newborn 7 – 12 years 130
Children 1 – 8 years 90
Children 9 -13 years 120
Adults > 14 years 150
Pregnancy 220
Breastfeeding 290

* The above values are according to U.S. Institute of Medicine.

Why Does the Iodine Requirements during Pregnancy & Breastfeeding Increase?

During pregnancy, the necessary intake of iodine increases due to some physiological changes. This is due to the increase in the synthesis of maternal thyroid hormones (up to 50%) to ensure enough amounts of hormones for both mother and fetus, which takes transplacentally some of these hormones that are synthesized by the mother. This mechanism is essential because during the first trimester of pregnancy; until the fetal thyroid is formed, the transplacentally transfer of thyroid hormones from the mother represent the only source of thyroid hormones for the fetus, which are very important for the nervous system and brain development. From the second trimester of pregnancy, once the fetal thyroid has started its function, some of iodine is taken transplacentally by the fetus for its own production of thyroid hormones. The necessary intake of iodine during pregnancy also increases due to the increased urinary iodine losses secondary to hyperestrogenism during pregnancy.

Women with an adequate prenatal iodine intake during pregnancy have adequate iodine deposits and don`t experience difficulties during breastfeeding to this increased necessary intake during pregnancy.

The thyroid may store 8 – 10 mg of iodine, which has the role of protecting the organism for a temporary deficiency. Still, in areas with even a moderate iodine deficiency, these deposits usually aren`t enough and have a tendency of dropping during pregnancy.

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During breastfeeding, some of iodine is secreted in milk to ensure the necessary iodine intake of the newborn. This is also the reason for which the necessary intake of iodine is maintained increased, being even higher than during pregnancy.

What Are the Sources of Iodine?

Some vegetables and water are good sources of iodine, but their content varies depending on the concentration of this element in the soil. Therefore, in some geographic areas with iodine deficit, the iodine intake from foods isn`t enough. In these areas, iodine supplementation programs was introduced in the diet by universal salt ionization as well as forcing some foods with iodine, like bread or oil. – Check this out!

The richest foods in iodine are fish (tuna, cod or mackerel), seafood or seaweed. Maternal milk has an increased content of iodine, which may ensure the necessary intake for infants.

There are a series of factors that may prevent the iodine absorption, such as:

  • Cruciferous vegetables (cauliflower, sprouts, cabbage or turnips), millet, manioc and sorghum, which naturally include some substances that have a competitive action with iodine;
  • The presence in water of some substances like nitrates, magnesium, manganese or calcium, as well as other minerals or organic pollutants, which aggravate the deficiency of iodine by competing with it in various mechanism.

Additional Supplementation of Iodine During Pregnancy or Breastfeeding

The practical recommendation that most doctors give to their patients is to start supplements of iodine with a dose of 150 µg/day with 6 – 12 months before pregnancy, which need to be followed through the entire pregnancy and breastfeeding period. In the case of pregnant women who didn`t prevented the iodine deficit prenatally, it`s recommended to take supplements of iodine of 200 µg/day during pregnancy and breastfeeding.

Consequences of Iodine Deficiency

Consequences of Severe Deficiency of Iodine

Severe iodine deficiency in an adult is accompanied by an increased number of cases of infertility, goiter, hypothyroidism or decreased intellectual ability. Regarding pregnancy, a serious deficit of iodine is associated with an increase in the number of miscarriages, premature births and low birth weight. Maternal or fetal hypothyroidism induced by a serious iodine deficiency has very serious consequences on the myelination and development of central nervous system, which are responsible for the appearance of mental retardation, endemic cremation with psychomotor retardation, speech disorders or deafness. A severe iodine deficiency is the main cause of mental retardation which might be prevented on a global level. Presently, it`s estimated that about 100.000 children all over the world are born with cretinism.

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Consequences of Moderate Deficiency of Iodine

The risks involve the development of goiter in the mother (15% to 30%) and of a hypothyroidism, which is frequently subclinical. This thyroid hypertrophy due to iodine deficiency is only reversible in part after birth, and can always relapse for every pregnancy, being a guogogenic factor when it comes to women.

A moderate deficiency of iodine in pregnant women is usually defined by a urinary iodine value of 50 to 150 μg/L during pregnancy and 20 to 99 μg/L when a pregnancy isn`t involved.

How Iodine Deficiency Diagnosed?

From an epidemiologic point of view, the most useful biochemical parameter for indentifying iodine intake in a population is monitoring urinary iodine median value.  In a population, we talk about an adequate iodine intake if the median urinary iodine is somewhere between 100 and 199 μg/L. During pregnancy, when the necessity for iodine intake is a lot higher, we are talking about an appropriate intake for median iodine value somewhere between 150 and 249 μg/L. From the epidemiological point of view, we can talk about a deficiency of iodine when the values of urinary iodine are below μg/L in the general population, and less than 150 μg/L when pregnant women are concerned.

Additionally to urinary iodine, there are also other parameters that can be followed: goiter frequency, thyroglubulin and the level of TSH. The criteria used in the epidemiological assessment aren`t fully applicable to individual cases because of large variations in the daily iodine intake and urinary iodine. If you are interested in finding out if you such from a deficiency of iodine, you`ll want to talk about it with an endocrinologist who`ll assess the presence of a few aspects of iodine deficiency.

Image courtesy of articles.mercola.com
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