Dangers of High Iodine Supplementation in Pregnancy

Marilyn Holasek Lloyd RN MALS

 A study was released last week from the Journal of Pediatrics, showing that high dose iodine in 3 infants caused hypothyroidism.  Now as studies go, this was a small study, but as it turns out probably a ground breaking one.

Here is a copy of the abstract and a link to the full study


All prenatal vitamins contain iodine because it is a necessary supplement for the well-being of a baby’s neuro-cognitive development.  This has been known for years and years.  Everyone needs iodine and especially now since iodine was removed from the making of bread and replaced with bromide years ago.  Bromide displaces iodine in the body.

But how did this happen that a supplement that was so needed by everyone ends up potentially hurting some babies?  Simply because iodine became a cottage industry:  Iodine books, Iodine articles, Iodine loading tests etc.

This is a good thing in the area of breast cancer prevention. There is great validity to the theory that iodine might play a vital role in breast cancer prevention, but the jury is out on the dose.  Some practicing alt meds and physicians have been recommending huge doses and have thousands taking them.  This is fine for consenting adults to be guinea pigs for the accepted doses of iodine, but it turns out to be potentially dangerous for the most vulnerable, the babies.

And simply put, the iodine craze filtered down to pregnant women.  Women who wanted their babies to be “smart.”  So they stepped outside the bounds of established obstetrical advice and started taking extra iodine without their OB’s knowledge.   The shame here is that the “iodine-literate” docs probably never studied the effect of iodine in neonates and newborns and didn’t disseminate a warning about excess iodine to pregnant and lactating women.

Frankly, my dear OB-GYN husband would have been appalled that this could happen.

Now, I think, in light of this potentially medically setting precedent, medical professionals will need to attach a warning on excess iodine in pregnant women.

And in my personal life, well-meaning people in the iodine community even recommended that my pregnant daughter (at the time) take iodine   I knew better than to interfere with obstetrical practice.  But that is why I am so passionate about writing about this.

Going back to the three infants in the study,  the mothers took 12.5 mg of iodine daily.  This seems like a minuscule amount compared to the doses proposed for breast cancer prevention and for breast cancer survivors.  (but it is over 10 times the recommended daily allowance)  But that amount caused major problems for these 3 babies.  When you view the full study, the first baby might have a messed up thyroid for life.  The other two babies were twins and their thyroid’s recovered.  The head physician of this study,  Dr. Connelly, writes: the immature thyroid glands of fetuses and newborns have not developed this protective effect and are more susceptible to iodine-induced hypothyroidism. Although infants recover normal thyroid function after acute iodine exposure (e.g., a few days of topical iodine application), continuous excessive iodine exposure to the fetal and neonatal thyroid gland may cause long-term harmful effects on thyroid function.

How did the doctors find this thyroid problem in the babies?  By routine screening of the newborns thyroid function.  It is such a well documented article with all of the tests the babies had including analysis of the mother’s breast milk.

Now here is what is really scary.  The first mother’s breast milk was loaded with iodine.

So this is a cautionary tale for both pregnant women and breast-feeding mothers not to take extra iodine.  A good prenatal vitamin which lactating women take along with their food (if they don’t go overboard with seaweed) will not give their baby’s this problem.

What makes this such a ground breaking study is this might be the tip of the iceberg.  My guess is that newborn thyroid screenings are going to show more of this problem.  At least all 50 states have a thyroid screening test.

How many well-meaning women are thinking they are doing the right thing by supplementing all that extra iodine, when it could be potentially  considered the wrong thing?   Dr. Connelly seems to be worried about this and this would include all obstetricians and pediatricians.

The take home message for all of these doctors is to get a straight answer out of their patients of exactly what supplements their patients are taking.

In America it seems, more is better,  but in the case of iodine supplementation, it has been shown to be dangerous for pregnant women and breast-feeding women to take overdoses of iodine.  The poor little baby’s thyroids can’t handle it.