One of the most serious effects of iodine deficiency is damage to a fetus. (Echo: Damage to a fetus…damage to a fetus…damage to a fetus.) Iodine deficiency wasn’t on my radar when I conceived last fall! I had had no dairy, no eggs, and no iodized salt for at least a year and a half, and I was taking no iodine supplementation, prenatal vitamin or otherwise. So I have to wonder about my iodine status prior to pregnancy and in early pregnancy. Early in pregnancy, I was too sick to tolerate a prenatal vitamin, and both my doc and I agreed that all I probably really needed to be sure to choke down was a folic acid supplement to prevent neural tube defects. (Strangely enough with the food and smell aversions, in my first trimester, I could not get over the urge to eat any and all kinds of seafood, which is a good source of iodine: sardines, oysters, mussels, clams, mahi mahi, tuna, shrimp, scallops, soft-shelled crabs, Nori, and dulse–you name it. I threw seafood cautions to the wind and gobbled that stuff down, since nothing else sounded good! Anecdotal but interesting.)
I wish someone would have told me that my best sources of iodine had all been removed from my diet, and even with them included, I would still have been at risk for iodine deficiency. So if you’re dairy-free, skipping iodized salt, vegan, intolerant or allergic to eggs, autoimmune Paleo, or follow a crazy diet (I can say that because I follow a crazy diet.), please just make it a point to make sure you’re getting sufficient iodine. And as always, don’t use anything on my blog as medical advice.
Not good. Statistics show that pregnant women’s iodine intake and levels are not sufficient and are continuing to decrease.
In the United States, there is a periodic survey which evaluates how our iodine intake is doing, the National Health and Nutrition Examination Survey (NHANES). NHANES has revealed that urinary iodine levels for pregnant and non-pregnant women in the United States have dropped significantly since the early 1970s. Adequate urinary iodine levels for pregnant women should be 150-249 micrograms/L (based on the World Health Organization standards). The United States has hovered around and then dropped below this point:
- 1971-1974: 327 micrograms/L
- 1988-1998: 141 micrograms/L
- 2001-2006: 153 micrograms/L
- 2005-2010: 129 micrograms/L (Goal is greater than 150 micrograms/L) (1, 2)
In the most recent survey, some regions such as California and Pennsylvania were alarmingly low, 105 and 125, respectively. And this doesn’t even take into account the interfering factors of halides in our food and environment which interfere despite levels of iodine!
So what does low iodine mean for pregnant women and their babies? (Not good.)
Iodine deficiency can lead to what is called “reproductive failure” in the female, which simply refers to repeated miscarriages and increased stillbirths. The more severe the iodine deficiency, the more the risk increases. One study showed that the frequency of reproductive failure was directly proportional to the severity of the iodine deficiency. Women who had iodine deficiency had twice the risk of reproductive failure. (There are many causes of “reproductive failure” besides iodine deficiency. Other nutritional factors such as selenium deficiency could also be responsible for reproductive failure. And aside from nutritional factors, there are many other causes, as well. So I am not saying, “Iodine is it.” Please don’t think that.) (3)
Known iodine deficiency effects on the fetus are numerous and include:
- Increased miscarriages (loss before 28 weeks of pregnancy)
- Increased stillbirths (loss after 28 weeks of pregnancy)
- Increased premature births
- Congenital anomalies (birth defects)
- Increased perinatal morbidity and mortality (increased bad outcomes and death occurring shortly before or after delivery)
- Cretinism (mental retardation with changes in stature, hearing–often a high tone defect, and sometimes the inability to use arms/legs due to severe rigidity)
- Goiters in newborns
- Hypothyroidism in newborns
- Mental retardation
- Lower IQ (3, 4, 5)
Medical literature supporting iodine’s role in producing a healthy, in utero fetus and subsequent neonate is NOT hard to find!
All degrees of iodine deficiency…affect thyroid function of the mother and the neonate as well as the mental development of the child. The damage increases with the degree of the deficiency…
Iodine deficiency results in a global loss of 10–15 IQ points at a population level and constitutes the world’s greatest single cause of preventable brain damage and mental retardation. (5)
When a mom is iodine deficient, iodine deficiency is passed on to the developing fetus who has NO way of getting iodine or thyroid hormone except through the mom. You are it, Mama.
When a woman becomes pregnant, her baby absolutely relies on the mom’s thyroid hormone, which requires iodine to be made. The baby cannot make its own thyroid hormone until later in the pregnancy, and even then, it still needs iodine provided by mom as the raw material for its own thyroid hormone production.
Iodine is 100% necessary for the production of thyroid hormone, and if it is not sufficient, then the mother and baby will be exposed to hypothyroidism (lack of thyroid hormone). Thyroid hormone is necessary for the function of all cells and is critically important for brain development, especially in a fetus and newborn. Thyroid hormone helps to make sure that the fetus’s cells grow, develop, differentiate, and express the right genes.
Most health organizations recommend about 150 micrograms of iodine daily for non-pregnant adults, but iodine needs increase when a woman becomes pregnant. To make more thyroid hormone to cover the baby’s needs, the woman needs more iodine. She also needs more iodine because during pregnancy, the blood filtration through the kidneys increases and extra iodine is lost in the urine during pregnancy.
It doesn’t end with pregnancy, either. Nursing mothers need more iodine because the iodine is transferred to the baby by her milk. The baby still needs iodine. (6)
The developing brain of the fetus is probably the most vulnerable target organ for iodine deficiency.
First Growth Spurt of the Brain
The developing baby’s brain has two major “growth spurts.” The first one is at 12-20 weeks (months 3-5). During this first one, the brain cells (neurons) are rapidly multiplying, moving to their correct places, and organizing themselves appropriately. Studies indicate that iodine repletion should occur by three months of pregnancy to prevent cretinism (severe mental retardation, deaf/mute, and effects on the arms and legs). Most of us in developed countries probably won’t fall into iodine deficiency enough that cretinism would develop, but I think it may be revealing in other neurological conditions as well, that getting the iodine levels back up in the first trimester is probably optimal. However, even if the first trimester is missed, iodine supplementation still shows beneficial effects in pregnant women and their fetuses.
The second spurt of brain growth occurs in the third trimester and doesn’t finish until the child is 2-3 years old! This spurt allows the cells that support the brain’s neurons (knows as “glial cells”) to multiply, move to their appropriate places, and to become coated with myelin. By the time of the second spurt, the baby has a functioning thyroid, so it doesn’t rely on mom for thyroid hormone anymore, per se, but it relies on mom for its source of iodine. If mom is not eating enough iodine, baby still can’t make thyroid hormone for itself and its brain. If mom didn’t get enough iodine in the first trimester, damages can still be minimized.
“Correction of iodine deficiency during the second trimester reduced neurological abnormalities, increased head growth, and improved the development quotient in a severely iodine-deficient area of western China. Correction at a later period did not improve neurological development, although there was a trend toward slightly larger mean head circumference and higher development quotients than in untreated individuals. ” (6)
There is a spectrum of how insufficient iodine levels affects the fetus.
“Mental retardation from iodine deficiency is not limited to the extreme form of cretinism, but instead extends over a broad continuum to mild intellectual blunting that may go unrecognized unless carefully investigated. Thus, iodine deficiency puts virtually everyone in the affected population at some risk for brain damage. Many studies have compared performance of iodine-deficient children with that of iodine-sufficient peers on standardized intelligence tests…iodine deficiency lowered a mean intelligence quotient by 13.5 points. In view of the many people living in iodine-deficient areas and their vulnerability to its effects on the developing brain, these numbers indicate a staggering public health problem. This and neonatal mortality, rather than goiter, have become the main reasons for advocating urgent correction of iodine deficiency.” (6)
Severe iodine deficiency and cretinism: The most notable and sad outcome of iodine deficiency, as it is completely preventable, is cretinism. I have read that early Alpine explorers would come across entire villages of “cretins” isolated in the mountains. These local pockets of population lived off of iodine deficient land, and it wasn’t until food started coming in from elsewhere and iodine supplementation was implemented in the 1900s that the incidence of cretinism was reversed. At the time, doctors and people in general felt it was something “in the air” or “in the water” of the valleys or perhaps a “genetic fault.” Cretinism presents with:
- Short stature
- Mental retardation
- Deaf and mute
- Spasticity of limbs (the arms and legs can draw up tight and not extend properly)
Mild iodine deficiency: Mild iodine deficiency effects are more pervasive and not as concrete to pinpoint. Children from low iodine pregnancies have been found to have:
- Lower IQs
- Elevated hearing thresholds/ hearing loss (4, 7, 8)
Dr. Jerome Paulson, chairman of the American Academy of Pediatrics council on environmental health says this in May, 2014 for NBC News:
“The brain development issues are very subtle and are not likely to be noticed in an individual child. It’s an issue for society as a whole when you have a large number of children who are not reaching their full potential.” (9)
If iodine deficiency is increasing in our pregnant women, wouldn’t congenital hypothyroidism in the newborn be increasing?
So as I typed this post up, I thought, well–if iodine deficiency is creeping up among our pregnant patients, then our babies should have a higher risk of hypothyroidism (low functioning thyroid). In fact, a month ago, my hairdresser was telling me about her good friend whose baby just wasn’t very active. They checked, and it was hypothyroidism. I’ve never really looked at or been notified about increases in newborn hypothyroidism (congenital hypothyroidism) in any of the journals I subscribe to, so I Googled it. (Because low thyroid function is SO detrimental to a newborn’s health and brain function, one of the tests mandated by every state in the newborn screening poke includes a test for congenital hypothyroidism.) Sure enough, there is a rise of congenital hypothyroidism. I cannot and will not say it is due to maternal iodine insufficiency because I think most health problems are usually caused by a combination of factors, but I certainly am suspicious about iodine deficiency’s role in this. In Krakow, Poland, before the introduction of iodized salt, 1 in 3920 newborns had transient hypothyroidism, and after the introduction of iodized salt, the rate dropped to 1 in 48,474. (2) Experts are also considering the roles of perchlorate (a toxic byproduct of rocket fuel and fireworks production) exposure, as these seem to be contaminating our environment and entering our bodies, interfering with thyroid use of iodine, and whether use of iodine-containing disinfectants at the time of birth could contribute. (2, 10)
So why don’t we just put our pregnant women on iodine and crank her up good?
Case studies show reports of hypothyroidism in significantly iodine supplementing moms: So you’re a natural person. You’re not afraid of supplements. You’re pregnant, and you think you’re going to run out and start loading up on iodine. Not so fast. There have been cases of congenital transient hypothyroidism in newborns from maternal iodine supplementations, at doses of about 12.5 mg. Whoa. I would never want a baby to have hypothyroidism from over-supplementation! On the other hand, I think this area should be explored better. Was the mom supplementing other important nutrients needed along with iodine? How transient would the hypothyroidism have been in the baby? If the mom had kept supplementing, would the thyroid disorder have stabilized naturally? But we don’t know the answers to these nebulous questions, and so I accept that too high of a dose of iodine in pregnancy may be dangerous to the baby as well! On iodine deficiency in pregnancy, it is probably best for the iodine naïve woman to err on the side of recommended amounts. (11)
Prenatal vitamins: Slowly, recommendations are moving toward making sure women get iodine in their prenatal vitamins, and word is getting out there. NBC News had a little blurb on their site about it in May 2014. But, in my opinion, the information still is not out there to women OR their obstetricians. I just don’t think obstetricians are aware of iodine deficiency numbers in pregnant women, and I would venture to say many (most?) obstetricians don’t look at the prenatal vitamins their patients take! Only about 50% of prenatal vitamins in the United States contain iodine! And if they do contain iodine, the iodine content may vary by up to 50% of what is on the label. (1, 12) The American Thyroid Association recommends that all prenatal vitamins contain iodine, 150 micrograms. (13)
Best to get iodine optimized BEFORE pregnancy: This is good, but I feel iodine sufficiency needs to be in place WELL BEFORE pregnancy! If our pregnant women are low, that must mean that our child-bearing population is riding completely on the edge. In addition, it may be that some of the ill effects seen with iodine supplementation have to do with the iodine status of a person in the long-run! So the more iodine sufficient a person is their whole life, the more they tolerate extra supplementation without conversion to hypothyroidism. Dr. Elizabeth Pearce et al report on a study from Sicily which shows that moms who re-introduce iodized salt in the first trimester after having been off of it for two years have markedly increased risk of mom being hypothyroid! However, in patients who had used iodized salt routinely prior to pregnancy for two years, the risk of hypothyroidism in mom was much less (although not absent). (14)
Iodine deficiency is absolutely a problem in many pregnant women. Iodine should optimally be sufficient in the first trimester, and unfortunately this is often a period when women are not aware that they are pregnant or they are too ill to take a prenatal vitamin with iodine or eat iodine containing foods. I think that brings us back to the idea that we are functioning, many of us as a population, on a near empty tank of iodine to begin with. Adequate iodine intake should occur BEFORE pregnancy. I hope you are taking note and continue to take inventory of you and your family members’ sources of iodine. Eventually, after I summarize why in the heck we need iodine, I will do a more detailed post on iodine content of foods. You can see some basic summaries of this in my previous iodine posts.
I would like to tell you that your doctor, especially your obstetrician, is up on this. And maybe they are. But I have a sinking feeling most are not. If getting pregnant is possible for you, it is best to start thinking about iodine intake today.
Sorry for the long post. Hope those interested found some tidbits to ponder.
1. Kathleen L. Caldwell, Yi Pan, Mary E. Mortensen, Amir Makhmudov, Lori Merrill, and John Moye. Iodine Status in Pregnant Women in the National Children’s Study and in U.S. Women (15–44 Years), National Health and Nutrition Examination Survey 2005–2010. Thyroid. Volume 23, Number 8, 2013. (Link to full text)
2. John S Parks, Michelle Linn, et al. The Impact of Transient Hypothyroidism on the Increasing Rate of Congenital Hypothyroidism in the United States. PEDIATRICS Vol. 125 No. Supplement 2 May 1, 2010. pp. S54 -S63. (Link to full text)
3. Dillon, J. C. and Milliez, J. (2000), Reproductive failure in women living in iodine deficient areas of West Africa. BJOG: An International Journal of Obstetrics & Gynaecology, 107: 631–636. doi: 10.1111/j.1471-0528.2000.tb13305.x. (Link to full text)
4. Cresswell Eastman and Michael Zimmerman. Chapter 20: The Iodine Deficiency Disorders. Thyroid Disease Manager. Online. Updated February 12, 2014. (Link to online text.)
5. F Delange. Editorial: Iodine deficiency as a cause of brain damage. Postgrad Med J 2001;77:217-220 doi:10.1136/pmj.77.906.217 (Link to full text)
6. John Dunn and Francoise Delange. Damaged Reproduction: The Most Important Consequence of Iodine Deficiency. The Journal of Clinical Endocrinology & Metabolism. 2001 86:6, 2360-2363. (Link to full text)
7. DeLong GR, Stanbury JB, Fierro-Benitez R. Neurological signs in congenital iodine-deficiency disorder (endemic cretinism). Dev Med Child Neurol. 1985 Jun;27(3):317-24. (Link to abstract)
8. Alida Melse-Boonstra, Ian Mackenzie. Iodine deficiency, thyroid function and hearing deficit: a review. Nutrition Research Reviews. 2013 Dec;26(2):110-7. doi: 10.1017/S0954422413000061. Epub 2013 Jun 12. (Link to abstract)
9. NBC News Online. Link: http://www.nbcnews.com/health/womens-health/pregnant-women-need-iodine-supplement-doctors-say-n113326
10. Richard S. Olney, MD, MPHa, Scott D. Grosse, PhDa, Robert F. Vogt Jr, PhDb. Prevalence of Congenital Hypothyroidism—Current Trends and Future Directions: Workshop Summary. PEDIATRICS Vol. 125 No. Supplement 2 May 1, 2010
pp. S31 -S36 . (doi: 10.1542/peds.2009-1975C) (Link to full text)
11. Kara Connelly, MD, Bruce Boston, MD, Elizabeth Pearce, MD, David Sesser, David Snyder, MD, Lewis Braverman, MD, Sam Pino, Stephen LaFranchi, MD. Congenital Hypothyroidism Caused by Excess Prenatal Maternal Iodine Ingestion. The Journal of Pediatrics.
Volume 161, Issue 4 , Pages 760-762, October 2012. (Link to full text)
12. Angela M. Leung, M.D., Elizabeth N. Pearce, M.D., Lewis E. Braverman, M.D. CORRESPONDENCE: Iodine Content of Prenatal Multivitamins in the United States. N Engl J Med 2009; 360:939-940February 26, 2009DOI: 10.1056/NEJMc0807851. (Link to full text)
13. Public Health Committee of the American Thyroid Association, Becker DV, Braverman LE, Delange F, Dunn JT, Franklyn JA, Hollowell JG, Lamm SH, Mitchell ML, Pearce E, Robbins J, Rovet JF. Iodine supplementation for pregnancy and lactation-United States and Canada: recommendations of the American Thyroid Association. Thyroid. 2006 Oct;16(10):949-51.
14. Elizabeth N. Pearce. Iodine in Pregnancy: Is Salt Iodization Enough? J Clin Endocrinol Metab. Jul 2008; 93(7): 2466–2468. doi: 10.1210/jc.2008-1009. PMCID: PMC2453047 (Link to full text)
Great overview of hypothyroidism in pregnancy adn a section on iodine: